Minutiae; It is all in the details…

Recently, I had a call about a local CL72 owner who was seeking help for his 1965 model Scrambler, which was having numerous performance problems. He was located in N. San Diego County, so I referred him to my friend Randy Troy, who lived just a few blocks away. Randy has had years of experience in working on all kinds of Hondas and was trained as a Porsche mechanic and worked at a Datsun dealer back in the 1970s. He has a deep understanding about the “how’s and whys” of how things work, but had never been hands-on with a 250-305 Honda twin before.

He began with a basic tune-up to get it up and running, but encountered problems right away. The carburetors would fuel foul the spark plugs quite quickly, so the first thing he did was to remove the carburetors for inspection and cleaning/adjusting. If you have worked on any Honda Scrambler, you know what a PIA it is to get to that left side carburetor for any kind of service or removal. In the past few weeks, he’s become proficient in doing that job!

With the air filter tubes off, he was watching fuel spitting back into the inlets, even at idle, which is never a good sign. The compression readings were about 130 psi, which is about 20 psi low. This generally indicates that the cam timing is slightly retarded (a half tooth, which is remedied by changing a tooth on the crankshaft, not the camshaft). Sure enough the cam timing was off. Fortunately, only a CL72-77 allows for the top engine cover to be removed with the engine in the chassis, which allows for cam timing verification and adjustment. 

With the top cover off and spark plugs removed, the first thing to do is to anchor the head/cylinder to the engine cases, by putting some short  sockets on the studs secured with some nuts. This keeps the top end from lifting when you turn the engine over. First you have to locate the master link on the camchain, then carefully disassemble it and string some wire through the ends. Loosening the valve adjusters takes the camshaft lobe load off the cam, so it can be positioned in a way that the flats on the camsprocket are level with the top of the cylinder head.

Once the cam position is set, you have to jiggle the crankshaft around with the camchain ends held in such a way as to allow the crankshaft to bring the right piston up to TDC AND the ends of the camchain towards the top to reattach the master link once the timing is set. There is a lot of fiddling around to get this all to happen, but Randy did achieve the goal and the cam timing was back to where it belonged. 

Once that was done, then the carbs got a long look. Randy noticed that there was wear and corrosion on the needle jets that might have caused some fuel spray problems. He was lucky to find a new set of needle jets at David Silver Spares, which arrived in a few days. Then he mentioned the other calibrations of the jets, which were not quite correct. He found #120 main jets and #40 idle jets in place of the normal #115 mains and #38 idle jets. On top of that he read out the needle codes, which turned out to belong to a CB72, not a CL72. The CB72s have a “power jet” fuel enrichening system which calls for a different needle taper. Stock OEM CL72 needles are NLA now so Randy had to order the oft-maligned Keyster carb repair kits, which come with new needles, float valve, gaskets, etc.

Keyster kits are made in Japan, but have been found to have incorrect metering needle tapers and poorly fitting float bowl gaskets in the past. When the kits came in the gasket issues apparently remained and the needles were of a different taper than the CB72 needles, so that might be a solution for the rich running. With new needle jets and Keyster needles, the bike ran too lean off the bottom end, but the fuel backflow problems at idle were solved. The needle clips were lowered to the bottom notches in order to richen up the transition from idle through mid-range, which improved fueling somewhat.

Randy also learned about the ignition timing vagaries associated with having the camsprocket controlling the spark advance curve. He set the initial ignition timing statically with a 12v test light, but discovered that running ignition timing often does not reflect the initial settings. In order to prevent over-advancing the spark timing, the idle timing had to be retarded back towards the T mark instead of the F (firing) mark. 

Changing the ignition timing alters the vacuum signal to the carburetor metering systems, which causes the mechanic to have to alter carburetor mixture and idle speed settings. The ignition timing and carburetor settings are inextricably intertwined and there is not that much you can do about the ignition timing without tearing the cam shaft sprocket out for repairs or replacement. There is inherent slop and inaccuracies with this camshaft driven ignition system that cannot be completely overcome with a used engine.

With new carb parts, many of the performance issues began to subside, but Randy feels like the bike is still a little bit flat in the mid-range, so he bumped the main jets up to #125 to see how it worked; especially when jetting for today’s alcohol-blended fuels.

After all this intensive work to exorcise the demons of this bike, his test rides have highlighted a 2^nd gear jumping out issue, which requires an engine removal and cases split to remedy the transmission woes.  Carb jetting is still a bit off, mostly due to a lack of available OEM jet needles for a CL72. Sometimes you just do the best you can with what you have and then give it back to the customer highlighting the known remaining issues and an estimated cost to fix them properly. Randy probably got paid about half of what the job was really worth, time-wise, but he was appreciative of the chance to learn all about the mysteries of the 250-305 Honda twins.

To paraphrase Forrest Gump’s comments: “Vintage Hondas are like a box of chocolates; you just don’t know what you are going to get.”

Orphan Exchange; a twin for a single

Those who know me well are aware of my fondness for the Kawasaki W650 models, which were only sent to the US market for two years (2000-2001). I have owned three of them over the past 9 years, with two 2000 models and the last one a desirable 2001. The 2001s had some subtle changes to the front axle, steering head angle, rear fender and were painted a lovely two-tone Dark Green over a Cream bottom portion.

Due to a plethora of bikes that have been coming and going in the past year, I decided to let the 2001 bike go and advertised it on the local Craigslist as well as once on eBay, but with no results. The bike only had 9k miles on it, was all dialed in with carb jetting and suspension upgrades and was driven briskly on Sunday mornings with my friends the Jamul-igans. With skinny tires and forks, plus about ½ of the other’s horsepower ratings, the bike was driven hard, but not abused. Previous crash damage was mostly all repaired; leaving only a few spots of scrapes and paint chips. It put a smile on my face every time I drove it, but it was a bit too big and ungainly for quick trips to the local Post Office or auto parts stores. Historically, I don’t keep vehicles much longer than a year or two, so the time was up for this fine machine.

Most of the Craigslist responses were scammers trying to get my email address or phone number for nefarious purposes, but one reply came from a man in Rocklin, CA (550 miles from Spring Valley) who was “ready to buy” and even considered flying down and riding it back home. The only holdup on his plan was that he was trying to sell his 1990 GB500 TT bike, which was somewhat weathered and had 29k miles showing on the speedometer. The sales efforts were non-starters for various reasons, so after we exchanged messages back and forth for a couple of weeks, I decided that I would offer a swap; his GB500 for my W650. He agreed to meet me “half way” between SV and Rocklin at Visalia, CA, where my cousin has lived for over 40 years.

The photos of the GB500 were less than detailed, but I figured that a licensed, running GB500 with mostly all original parts was equal in value to what I was trying to get for the W650. So, one Friday morning, at 4AM, I launched my Toyota Tacoma up the I-5 with the Kawasaki W650 secured in the bed. The plan was to get through LA traffic before it became unbearable during rush (?) hour. I had agreed to meet up in Visalia at noon time, to give us both plenty of time to arrive at the destination. Well, my plan was a little too optimistic, perhaps, as I arrived some 300 miles from home at 9:30AM!

Texts from the GB500 man indicated that he didn’t leave Rocklin until 6:30AM, which took him right into downtown Sacramento traffic at 7AM, so he was delayed quite a bit on his end of the journey. 

In the meantime, I spent time with my cousin who owns a thriving auto repair shop in Visalia and is a real “gearhead” kind of guy, owning a couple of 1960s Mopar drag cars equipped with Hemi engines, as well as an airplane and some pricey automobiles and trucks. It was great to catch up with him during my 3 hour stay, but I finally decided to leave the shop for the rendezvous near the Highway 99 Junction which was about 8 miles away. While I was driving, he sent a text indicating that he had taken the wrong off-ramp and was turning around to the intended location. As I came upon that same off-ramp, I looked ahead to see his car (Honda Element) just getting back on the freeway. I went back on the freeway ramp and followed him right to the Chevron station that we had agreed upon as the meeting place. Good timing!

Yes, the GB500 came down in the back of a Honda Element SUV, actually fitting in quite nicely. We unloaded our bikes, took a quick test ride to confirm that this is what we really wanted to do, then swapped bikes into each other’s vehicles, completed paperwork and headed off for home, once again.

I was a little disappointed with the overall condition of the GB500, as the alloy parts were mostly corroded, however most of the chrome plating was relatively clean. Apparently the bike lived in Oakland for awhile, near the bay and was obviously ridden a great deal in the past 27 years, so wear and tear is expected to a certain extent. My biggest concern was the noises coming from the engine, as it was fired up cold. It was hard to pin down the specific area of the engine where the noises were occurring, but it was a bit unnerving to say the least. The bike ran fine on the test run, so I just decided to go forward with the deal and fix whatever was necessary later on.

I ran back down the 99 to the I-5 junction, then up over the Grapevine pass to the 210 highway junction, which I took to my friend Myke’s place in Sunland, CA. The total mileage covered for the day was about 500, all in 13 hours. I enjoyed some rest and a nice Thai meal nearby and went to bed planning on an early start on Sat morning, in order to miss the always busy southbound freeway traffic headed into San Diego.

I launched at 6:30AM and headed way east towards the I-15 southbound, where traffic was racing along at 70-85mph, making the return leg of 180 miles in 3 hours. I unloaded the bike, unpacked and then stripped the tank off of the bike to see what was underneath the bodywork and perhaps pin down the source of the engine rattle. With the help of S100 cleaner and a hose, I was able to clean the bike up pretty well, followed by a blow-dry session with the air compressor.

I checked the valve clearances, which were just slightly loose and attended to an odd oil leak that was coming out of the center of the rocker arm cover. The bolts for the cover are all supposed to be dry, so I was able to squeeze a little 8mm o-ring over the bolt head (it was too long to remove with the engine in place) and then retorqued the bolt, hoping for an effective repair of that problem. I finished up by installing a fresh spark plug and removing the rest of the pollution control devices and hoses which were partially taken off by the previous owner.

Both tires were under 20psi, so I aired them up, checked the oil level and the chain tension and headed out for a test ride around the neighborhood. The bike ran well and was responsive to the throttle, but the clamor coming from the engine continued to puzzle me. I decided to take the GB500 on the Sunday ride and see if it would break something or if the noises were just excessive piston slap on a 92mm wide piston, churning up and down with a redline of 8k rpms.

Well, the Sunday ride went well and I thrashed it as much as was reasonable under the circumstances. Unfortunately a prior owner installed oversized tires on both ends, so a good deal of caution was taken not to get them way out on their sidewalls. The tires are Bridgestone BT45s, which are grippy things, but these were getting sidewall cracks due to age.

Back home, after the ride, I did research on the GB500 noise problem and found a detailed webpage that described having to replace the piston at 27k miles on his machine, plus he rebuilt the crankshaft with a rod kit which is available. The engines are related to the early XL/XR500-600s, so some of the parts will interchange. Supposedly, the 97mm XL600 piston and cylinder will mount up on the GB500 cases, giving a 100cc displacement increase. Other models use a 100mm piston, but that is probably really pushing it, unless you do a full-on rebuild.

Top end teardown

After the successful Sunday ride, I decided to drain the oil and pull off the top end to see what might be causing some of the noises inside the engine. Fortunately, the top end can be removed with the engine still in the chassis. You can pull the head off and away from the carburetor/manifold/air box with those components all safely in place.

The top cover has the rocker arms all installed and the first bit of bad news was that both of the exhaust rocker arm pads were worn down excessively. The good news is that the intake sides were all just fine. The center of the cam runs directly on the cylinder head bearing, which is oiled by an oil feed hole in the camshaft. The cylinder head side was scored and roughed up like the exhaust rockers, but the top cover bearing surface was like new.

After figuring out how to extract the camshaft from the sprocket and two ball bearings, the head was ready to remove. There didn’t seem to be a lot of deposits or moist carbon on the valve heads or the piston crown, as if someone had been in there before, freshening up the internals. Sure enough, despite a lack of markings on the piston, the piston rings had .25 marked on the edges. The piston didn’t show any signs of distress or a great deal of wear. The cylinder bore still had nice cross-hatch marks on most of the surfaces, but when the rings were removed from the piston and stuck back into the bore, the end gap was .025” to .035” on the two top rings. Normal specs are about .012” to .016” using the standard reference of .0045 inches of end gap per each one inch of cylinder bore. I had my machinist friend measure the piston and bore size accurately and he determined that the piston clearance was about .003” which is near the wear limit of .004” that Honda recommends. He felt that the piston clearances were not sufficient to create the kind of engine noises that I was hearing.

With the 24mm piston pin removed from the piston and refitted to the rod end, it was evident that there was enough clearance to give a loose rocking fit to the pin in the rod end. Most likely, this is the main source of the engine noise. The remedy is to install a $125 rod kit in the crankshaft, once the engine is pulled all the way apart and a machinist presses the crank apart and back together again with the new rod kit. Not what I had in mind for this little bike project.

All apart…        

The bottom end was pulled out of the chassis and put on the bench for disassembly in order to replace the connecting rod in the crankshaft. There are several locking nuts inside to secure the clutch hub and other critical components, which needed a 24mm socket and air wrench to remove. Once the locking nuts were removed, the rest of the engine more or less melts apart into transmission and counter-balancer units along with the huge ball bearing which supports the crankshaft in one case half.

While waiting for the arrival of the connecting rod kit, cleaning and some painting was done to the top end components, along with replacing the valve stem seals in the head. The valves were de-carboned and the combustion chamber cleaned up of old burned oil residues. The inside of the engine was quite clean, so regular oil changes must have been done in the past 27 years. New gaskets and seals were procured via the Internet, but it was surprising how few parts are left available for these bikes now.  A SoCal dealer had a new set of .25 oversized rings, which when checked in the cylinder bore did show a reduction in the end gap measurements over the old ones removed.

A local camshaft manufacturing shop felt they could regrind the lobes without having to dig too deep into the base circle (schneidercams.com) so they took the old camshaft in for a couple of week wait in their queue. New OEM rocker arms were purchased through the local Honda dealer, so the major pieces are coming together finally.

Because of the miles on the bike, a decision was made to buy an aftermarket starter motor repair kit and freshen up the starter motor before it was returned to the engine cases. Once apart, there was very little wear showing on the brushes, so the kit was left unopened and will go with the bike to the next owner someday in the future.

The carburetor still hung in the airbox, so it was an easy task to remove the throttle cables and enrichener, loosen the clamp and remove the whole carb as a unit for cleaning and inspection. In all likelihood the carburetor had never been serviced as it was still jetted to the CA spec 142 main jet size. I didn’t have any 145-ish jets handy, so used my tapered jet reamers to open it up more towards a 148-150 size. With a fresh motor, use of alcohol-based gasoline and the possibility of a slightly modified camshaft grind, a little more fuel is generally a good step towards improved performance.

The crankshaft was taken to a local machinist friend, who found difficulties in attempting to remove the crankpin from the assembly due to a close-fitting sprocket pushed up against the crankshaft cheek. Finally, he just pressed the easy side off and checked the pin for wear and damage. The pin checked out fine, so the new rod was installed and the crankshaft pressed back together again. Finally, he had to gently press the crankshaft back into the engine case half to complete the job.

With the crankshaft done, assembly work could resume and all the little bits and pieces reinstalled where they belonged. 

I had the unfortunate experience of buying an “Engine bolt kit” from an eBay seller which appeared to be a complete kit, but was found to be missing the crankcase bolts. Emailing back to him was frustrating as I was told that if I had “read” the details I would have seen that the crankcase bolts were not a part of the “kit” and were available at an extra, undefined charge. This was all buried in a dozen paragraphs once you hit the “SEE DETAILS” section. Why he chose to offer a “kit” without the critical center case bolts is a mystery and he never would say why he did it or why he didn’t list the price of the extra bolts in his auction. After some unpleasant exchanges, I paid an additional $25 for a handful of bolts, which the seller then cancelled and decided to block me from future business, leaving me without the final matching bolts to finish putting the engine back together with.

Another seller on eBay did offer the center case bolts as part of their main kit, but I only needed the few not a whole kit. His main website offered individual bolts and fasteners in an easy to use menu, so I ordered up what I needed from there and awaited delivery. It was a very frustrating experience to say the least and has held me up an extra week, just because the seller decided to play games with his product offerings.

In the meantime, the front brakes were addressed with a caliper rebuild, new pads and a fresh master cylinder kit installation. New BT45 tires were spooned onto the rims and fresh rear wheel dampers installed in the rear hub.

Drama and Difficulties

After several weeks, the cam grinding company discovered that they couldn’t grind the cam lobe next to the de-compressor parts attached, so took it to a nearby machine shop which took 2 tries to get the end pieces pressed off. Apparently they only had an arbor press not a hydraulic one. They finally get it loose, with the bits flying all over the floor. They claimed to have found them all but later on I discovered that the thrust washer was not in the bag of bits. With the de-compressor parts removed, they were able to grind the cam and Parkerize it afterwards. When I took it back to my local machinist friend’s shop we discovered the missing thrust washer. I ordered a new one from Honda, but the only ones were in warehouses back East and it took a week to get one out to SoCal. In the meantime I found that the oil filter washer from a CB750 was about the right size, so I used that when the parts were pressed back onto the end of the camshaft.

I thought I was near completion when I discovered that the funky cylinder head-mounted camchain tensioner requires a Honda special tool in order to retract the tension from the camchain guides. The tools are available for about $50, so I ordered one of those, too. In the meantime I tried to wrestle the engine back into the chassis by myself and fought it for more than an hour before it finally found just the right positioning to get the mounting bolts installed. The only other GB500 engine install I have done was when I lived in Hawaii and that time I wound up laying the engine on the floor and dropping the frame over the engine so I could get the alignment done. It is a total PIA and the frame tubes are all scratched up from the wrestling match efforts.  Apart from flywheel pullers, I have never had to use a special tool to reassemble a Honda engine until this one. Nevermore!

On the home stretch…

From the time the bike was picked up, it has been almost exactly 2 months of work and waiting to get the GB500 back up and running again. After several weeks of waiting the camshaft was ground, but the result was that the de-compressor gear really didn’t want to work with the re-profiled cam lobes, so the whole assembly was removed from the camshaft. Apparently only the US versions of these bikes had one in the first place, so no big deal to remove the de-compressor parts.

Just as I thought the end was in sight, the first firing of the engine revealed a pair of exhaust leaks. I had ordered the wrong head gasket (XR500, instead of the one for the GB500) and it didn’t have the extended sections to encompass the PAIR (pulse air) system transfer ports! It took another three hours to R&R the cylinder head gasket to repair the exhaust leak problem. Once that was finally accomplished, the bike fired up once again and seemed to be running well.

Several local road tests failed to reveal any major further issues, so the bike was taken out on our Sunday morning rides up into the mountains and back, about a 65 mile round trip. With scuffed in new BT45 tires, new front brake system overhaul and new pads, everything is getting a new break-in period, but so far it seems to have been a success in the end… but what a lot of work and expense!

Benly BIG-time Blow-up

The whole CB92-CA95 (US models) line up was a lightning bolt into the hearts of other manufacturers during the late 1950s and early 1960s. These tiny electric-start 124-154cc twins would spin up to 10,000 rpms, when pressed or just doddle along at traffic speeds without complaint, in most cases.

The engines were 360 degree firing parallel twins with a short 41mm stroke, two-valve cylinder head design operated by an OHC camshaft. The camchain ran off of the left end of the crankshaft sprocket, over a guide roller and through an adjustable camchain tensioner. The 4 speed transmission was a normal return change design, operated by a 5-plate light-pull clutch assembly. The back of the clutch basket was machined with an eccentric that connected a flat steel arm which worked a push-pull plunger inside a cast steel oil pump body. The whole design was elegantly simple, but built with precision and quality materials.

A weakness in the design of the crankshaft became evident early-on which required several different crankshaft changes. The main differences started with the 1959-90 crankshafts which had a larger center main bearing than the two on each end. Initially, all three bearings were located in the engine cases with the “half a piston ring” retainer.

In 1961, the center main bearing was reduced in size to match the other two and the bearing was located with a dowel pin to keep the oil feed holes in alignment. The end bearings were still retained with half rings, which allowed them to rotate in the cases at very high rpms.

 The engine cases were also slotted to help facilitate oil moving over to the crankshaft in one design. On early CB92s the engine case slot (at the rear of the cylinder base) lead to a low cut window in the back of the left cylinder liner to help lubricate the piston skirt, which apparently was not getting enough oil. This lack of lubrication caused piston seizures and subsequent crankshaft failures when the connecting rods were brought to a halt suddenly.

The 1962 crankshafts used pinned bearings all the way across. The rotor side main bearing of the crankshaft was a caged-roller style with a thrust washer, while the transmission drive gear end used a ball bearing. Some versions had a larger diameter end bearing, as well.

The current repair bike in the shop was a low-miles, mostly original, 1961 CA95 Benly with engine number #59. The owner had owned it for a few years and put less than 1,000 miles on it but the engine began to smoke a lot from one side, so the top end was freshened up with .50 pistons/rings and a valve job. Right away, the owner reported that the bike lacked the snap of his other Benly 150 and wouldn’t go faster than 45 mph in top gear. In the middle of a ride, the engine slowed down, seized up and began to make some unpleasant knocking/rattling noises when restarted.

Having owned a handful of CB92s, plus a 150 Benly or two, I was fairly comfortable doing a forensic exam report on the engine after it was transferred to my custody at a VJMC event held in Solvang, CA in Sept 2017.  Once it was on the bench the engine was removed and the teardown/inspection process proceeded. The drained oil had a lot of bright shiny particles in it, which is never a good sign. The ignition timing was checked to eliminate that as a source of the piston seizures, due to detonation from too much spark advance. The top cylinder head cover was removed to view the valve train which all seemed to be in good condition, but still flecked with brass-colored particles here and there.

The cylinder head was lifted off and set aside for further inspection. The cylinder bores seemed to be relatively unharmed, apart from some superficial wear/scratching. Once the cylinder block was lifted off, the serious damage began to be revealed. There were a couple of missing pieces from the bottom of the left piston skirt and both pistons showed signs of repeated piston seizures in the past. When the left side connecting rod was checked, there was noticeable up/down play which shouldn’t be there at all.  A few pieces of the piston skirt were lying just below the pistons on the crankcase bosses and more of that shiny brass particle debris became evident.

The camchain, stator and left side engine covers were all removed to facilitate engine case separation. When the clutch cover was removed on the right side, a stream of contaminated oil gushed out of the hidden nooks and crannies all laden with large amounts of brass filings and particles. There seemed to be more brass residue than was possible from just one rod bearing failing, but that was about all that could be seen as a source. The entire engine was contaminated with metal particles, including the oil filter. The clutch was removed, along with the oil pump which is driven off the back of the clutch basket eccentric.

The engine cases split without too much difficulty and more metal debris poured out onto the work bench. The transmission gears seemed to be in good condition; however one of the locating dowels for the transmission bushings was half bent to one side, due to a shearing force on the transmission shaft. There were more questions than answers, but one thing was for sure; the crankshaft and pistons would have to be replaced!

Continuing the repairs…

A lot of cleaning has taken place to expunge all of the little brass particles that were circulating around inside the engine before it finally expired. The oil filter, which spins on the end of the crankshaft, was packed with colored bits of course. Top and bottom cases were cleaned thoroughly as were all the clutch parts and transmission gearsets. Rather than replacing the hollow dowel pins on the transmission shaft bushings, a couple of 6mm crankshaft roller bearings were ground down to a matching length and secured into the top case half, which was lying on its back awaiting newly freshened parts.

The crankshaft replacement really only had used parts options, as new crankshafts are NLA in much of the world. A $135 (delivered) used crankshaft from an eBay seller came with the rotor and left cover as the seller was unable to pop the rotor off the end of the crankshaft during teardown.  After measuring all the crankshaft main bearings, it was discovered that Honda had increased the bearing size on one end. The old crankshaft mains were in good condition so the end main bearings were switched from the old crankshaft to the new(er) 1964 part. That swap was successful and the updated crankshaft was placed into the cases. Although the engine had been freshened up within the past couple of years, new seals were ordered along with a fresh gasket kit. The oil pump was cleaned and inspected for damage, then the small ball spring replaced, along with a new o-ring for the pump’s side plate.

Fortunately, the cylinder bores (bored to .25 oversize) cleaned up to like-new condition, so fresh pistons and rings will have a nice new home to work within. A correct slotted base gasket was discovered for sale on eBay, so the oil channel will have a maximum flow rate to the center main bearing. The original base gasket was the later model flat version, normally used with engines which do not have the oil channel, so there might have been some flow restriction at that point.

The cylinder head had little debris, apart from the inside of the camshaft oil feed hole. The cam lobes and rocker arms were unharmed. Spray cleaner was used to check for any valve leakage, but none was found, so the valves, which had been replaced earlier, were left undisturbed.

Still looking for the “smoking gun” that caused this disaster, the carburetor was inspected for jet selection. The main jet had been increased one jet size; however this carburetor has “power jet” enrichening circuits which are controlled by two tiny air/fuel correction jets. With information gained from the Facebook Vintage Japanese Bike Club subgroup, which is focused upon the CB92 (Super sport version of the CA95 Benly), a member from Sweden offered up a specification page from an ancient manual showing that the jets for the power jet system were #130 in both locations. When the fuel jet was removed from the carb body, its size was not marked at all. The air corrector jet at the top rear of the carburetor body was stamped #130. Using a metric drill bit set, I determined that the inner jet was a #150 size.

Honda seems to have determined that these jets were not to be altered, so no references to the part number or sizes can be found on current online microfiches or even in my 1966 CB92 parts manual. Digging deeply into arcane parts references books, a part number was discovered that might have been correct for these jets. The ones listed in the book were not #130 size, according to the part number suffix, but substituting the end numbers with 130 got me closer to a source for them. While an eBay search for “air jets” revealed similar jets which fit CR250 motocrossers and GL1000 Gold wings, they are all ISO thread pitch jets. A 1961 CA95 Benly is all JIS thread pitch built.

Doing a web search for the desired part number revealed that it had been superseded and used in G30 Honda generators and early Honda 360-600cc twin cylinder cars. 

Fortunately, I live nearby a Honda 600 car guru, who has tons of used parts. I ran the part numbers and descriptions past him and he came up with a #120 air jet from an AZ600 carburetor! The jets matched up dimensionally and on the thread pitch, so I gratefully brought it home and reamed it out to #130 size using tapered jet reamers. Right or wrong, at least the carburetor was now close to specs for that power jet system.

The previous mechanic had contacted me, asking about my findings, as well as giving an overall view of what he had done and found previously in this engine. He mentioned that the carburetor needed some massaging to get the slide to stop sticking and I noticed that the carb flange was somewhat warped, even now. Obviously any air leaks at the intake flange are potential causes for piston seizures due to lean mixtures causing piston overheating.

Honda’s specifications for spark advance are puzzling as they show a range from 34 to 47 degrees before top dead center. In comparison, a CA160 has a 40 degree maximum spark advance range. I chose to squeeze the stopper ends of the advancer closer together in a vise, so that the maximum spark advance will be somewhat reduced. Over-advancing spark causes piston overheating, usually resulting in piston seizures, particularly when the piston clearance is only about one and a half thousandths of an inch.

Newly installed pistons and rings on a fresh rebore need some “break-in” time, which I suspect didn’t happen previously. Honda usually specs about 500-600 miles of easy riding before extended full-throttle is used. The engine’s last repair work didn’t include case splitting, only a bath in a solvent tank to remove thick layers of sludge from the bottom of the cases. When the cases were split, the sealant wasn’t familiar looking to me and someone had painted the number 78 inside the case halves! One can only guess as to whether the 78 marked the year when it was taken apart or some mechanic’s ID number or something totally different!

Having looked at each and every part of this engine assembly, I have confidence that it can become fully functional as designed, given a proper break-in period and judicious checking of the oil levels, ignition timing, carb jetting and use of the correct heat range spark plugs. The old spark plugs were not present in the engine, as a pair of C6HA plugs were loosely screwed into the cylinder head. Honda specs for the small 10mm plugs, used on the 1960-61 engines is a C7HA plug, which is a heat range cooler than what was supplied.  I will fire the bike up and ride it gently on the C6HS plugs then switch to C7HSA plugs for extended riding during initial break-in runs.

I’m not sure how long the bike was down since the blow-up, but the battery fluid levels were near the tops of the cells and measured voltage was 1.4v. An overnight charge brought it up to 6.66v initially, but started to fall to 6.4v later in the day. With only 6 volts available to power these bikes, you need everyone you can corral.

UP and RUNNING, but not ready yet

I was able to get the bike started up and ran it around briefly. Lingering problems exist in the fuel delivery and clutch. The engine ran well at low speeds but started to break up as throttle was increased. One issue was a bad spark plug cap connection on the right side. I tried jetting the bike down once to see if the oversized-main jet was too rich, but it got worse and responded to adding choke under power. I then took a jet reamer to the #100 main jet and opened it up to about 105 size. The bike has stock mufflers, but no baffles installed so jetting must be compensated for those changes, as well. The bike began to run much better and then the aftermarket clutch cable broke.

Both the clutch cable and throttle cables were too long and are old Dixie/Superior branded parts of less than wonderful quality. So, I needed to track down some correct cables for the bike, which were found on eBay; real ones this time, not reproductions. eBay sellers came up with actual OEM correct gray cables with grease fittings installed, plus the little tensioner springs were included.

The clutch drag continued, even with correct adjustment. I have to do research on whether the clutch pack wound up being too tall and that changed the angle of the clutch lifter arm and/or the clutch adjuster threads are worn out and we are losing pushrod travel because of that.

I had to replace the oil filter with a later model version due to the change in crankshaft designs. So far the engine sounds great, doesn't smoke and isn't making any unusual noises or leak oil anywhere.

 More work and more research and good results

The OEM Honda clutch and throttle cables came in quickly and were slowly replaced. Working on a Benly requires a bit of watchmaker and puzzle solver in order to fit all the small bits back together again. The cables must be routed through the pressed-steel chassis holes and meet up with their end point connections.

With the clutch cable installed, the clutch adjuster was checked for excessive play, but nothing out of the ordinary was observed. The throttle cable required the same feed through the chassis holes and then the cable end connected to the carburetor top components. The main jet was removed and opened up further, followed by another test ride. While the engine continued to show more power the clutch continued to show signs of dragging, despite all the cable adjustments being done correctly.

All that was left was to drain the oil and remove the clutch cover (after the exhaust system) and take a look at the clutch release function at the end point. Pulling the clutch lever in, at the handlebars, showed a restricted clutch release travel at the plate set, when the assembly was all together.  The feeling at the lever was that perhaps the clutch springs were coil-binding at full travel. Honda didn’t design that kind of problem into this model and this one shouldn’t be coming to a hard stop at the handlebar lever.

With the springs and spring plate removed the clutch travel seemed to increase. All the clutch plates were checked for thickness as one odd one was in the pack. Most of the correct plates measured out around 3.4mm, but one was at 3.0mm and a different type with thinner friction material. The PLATE A was a thick alloy piece, which was changed in later models to a different design along with a different center hub.  David Silver Spares came up with a correct friction plate, steel Plate A and outer pressure plate. The pressure plate showed some warping when the clutch pack was spun by hand. There were two low spots on the plate surface, as well.

The clutch spring retainer plate has a central hole, which is a stamped steel piece which is punched through creating an offset hole that matches the one on the outer clutch pressure plate. Putting the plate on with the offset outwards appears to cause some unnecessary binding of the plates when they meet in the middle. Turning the plate around so the offset nestles down next to the pressure plate’s center allows a more full travel of the plate set. With a correct set of friction plates, pressure plate and Plate A, the clutch should resume normal function and travel once again. A rough reassembly using the old parts showed increased travel/plate spread when the outer support plate was installed correctly. I discovered some Barnett Kevlar clutch friction plates in a box which fit the clutch hub on this bike, so it is getting treated to a hopefully bullet-proof clutch pack to carry it into the future.

When received, the steering head bearings felt notched and self-centering; so the bike just wanted to go straight ahead all the time. Removing the handlebars and mount allowed access to the top plate stem nut which was tightened with a great amount of force. Backing off the nut allowed the stem bearing nut to be loosened slightly and suddenly the steering felt transformed back to a normal feel once again.

The drained oil showed minute traces of stray flecks of brass and some fine powdery grains of steel being loosened and held in suspension by the Honda GN4 oil. The second cleaning of the filter showed almost no brass particles now. It appears that the updated, used crankshaft transplant has been successful, but not a completely easy task. Still, with the inventories of new crankshafts exhausted, selective use of the newer versions seems to be a viable alternative.

The final test rides showed a normal pull clutch lever feel, good power through the rpm range and a very slick feeling transmission function. The owner was very pleased with the results in the end.

This has been a thought-provoking and time-intensive project from start to finish. Some $600 worth of replacement parts have been purchased to date, along with a great deal of research time online for parts and hands-on labor to R&R the engine, tear it down, inspect and clean all the parts and order the correct replacement items to bring the bike back towards the original running condition. To paraphrase, “You learn the greatest lessons on a Honda!”

Score four and many more to go… last installment!

A little backtracking here, to catch up with the final repair experiences and eventual sale of all four bikes!

1965 CB77 Notes

While it looked relatively intact and came with a set of correct type mufflers, this bike obviously sat around for many years and had numerous surprises in store for me.

The first thing to do was to try to remove the seat…. It wouldn’t come off even though the rear seat bolts were not installed… ???  When I grabbed the right edge and lifted, the seat pivoted up on some home-made seat hinges, just like those on the later CB350-450s!  Well, that’s really different!

With the seat up on the side, the fuel tank was removed after cutting the fuel lines with clippers. There were no air filters or tubes present, so I stuffed some plastic bags/rags into the intake ports and rolled the bike over to the front yard gravel bed where it was soaked with S100 cleaner and hosed off. Some compressed air dried off the chassis and work went on from there.

The dipstick had dirty looking oil on the stick so an oil change was in order. I removed the bolt but NOTHING came out! Probably not a good sign, is it?  The clutch lever was a two handed effort to move even slightly, so the first place to go was the clutch cover. Once removed, some oil started to trickle out however.  On a hunch, I pulled the whole oil pump and a quart and a half of stinky old oil rushed out of the crankcases. Looking at the oil pump screen and drain plug, there was a thick layer of gooey black gunk covering the parts enough to actually block the oil from draining out of the drain hole! ICK! The insides of the crankcases, behind the clutch assembly were scaly black like old gasoline and oil had evaporated on the surfaces. I lifted the oil filter and chain off of the engine and was dismayed to find that the crankshaft nut was never fully tightened (plus the conical washer was on backwards), so the filter chain sprocket was just spinning easily and not driving the filter at all. At least someone had taken time to bend the locking tab over so the nut didn’t fly off the end of the crankshaft!

The clutch plates peeled off without too much trouble. Everything was washed with paint thinner and the steel plates run on a wire wheel to scrub up the surfaces. Everything went back together without issues, but special attention was given to the locking nut and washer/sprocket placement. With the cover back on and the oil pump scrubbed up, the pump was reinstalled. A ½ quart of Marvel Mystery oil was added to the crankcase, followed by a quart of Honda GN4 10-30 oil in hopes of dissolving the sludge inside the engine.

The carbs were removed and cleaned, but there was evidence of water getting into the left side carburetor at some time. When the carbs were removed, there were a lot of chalky deposits found inside the intake port on the left side. There wasn’t any sign of water/rust on the old spark plugs, so one has to imagine that the intake valve was closed when the water backed up into the port. Use of some penetrating oil called ACF50 seemed to dissolve the deposits in the port and I could push my finger all the way down to the back side of the intake valve to help clean things up. Still it is a pretty sketchy proposition as often the back side of the intake valve will have a rust buildup on the back side that will eventually get sucked into the cylinder when the engine is running. Initial compression readings were 150 psi on the right and only 90 on the left side.

Phosphoric acid was used on the float bowl and a few other parts to neutralize the scale deposits and the carbs were checked over and reassembled with new o-rings on the carb flanges and the insulators. The petcock was cleaned out and showed signs of perhaps being a NOS part due to some very shiny surfaces inside. The carburetors were also in very good shape with no wear on the chromed brass slides whatsoever. Carbs and petcock were installed back on the bike and a fresh battery inserted into the frame holder.

There was a fuel leak on the left carburetor that seemed to be due to a compressed float bowl gasket and not enough tension on the bale spring. A new bowl gasket was slipped in place on top of the old, glued-in version and the leak stopped. With full choke ON the starter button did nothing when depressed. Looking at the overall condition of the bike, I surmised that the electrical contacts were probably all fuzzy and corroded, but cycling the starter button a few times began to wake something up. At first it was just a click, then the sounds of the starter motor engaging briefly. Continuing to push the button finally created a complete circuit and the engine spun over vigorously and finally fired off on both cylinders!

Letting it run for a few minutes at low engine speeds, I listened for any signs of damage or impending seizure due to a lack of oil, based upon what I saw draining out previously. The engine seemed to be fairly healthy and after some initial smoking the exhaust cleared up completely. Pulling the spark plugs there were no signs of any engine distress or ingesting anything damaging. Compression readings rose to 120 on the low side, which was promising to say the least.

I had already replaced the apparently original stock OEM front tire and the silly 3.50x18 Trials tire on the back with correct sized Michelins. The clutch cable was replaced along with the worn out clutch adjuster which brought a reasonable lever pull effort back into play. The front brake cable came from old stock, so the main control cables were now functioning properly.

I took it for a brief test ride and didn’t notice anything amiss, so gradually lengthened the ride time and distance out further. The bike had come with some aftermarket shorty mufflers, but the deal included some OEM type mufflers which were installed. The right side was an old Dixie International “Superior” CB77 copy which didn’t fit quite right but looked the part. The left side muffler was an OEM 2 piece muffler which was in good shape apart from some battery acid stains on the inside. There were no baffles in either one, but the overall sound was tolerable for the neighborhood.

After a couple of rides, I checked the oil and the end of the dipstick was BLACK! I warmed it up once more and then dumped the oil out of the drain hole successfully. The Marvel Mystery oil was definitely doing its job so far, but I refilled the crankcases with straight Honda oil this time.

This is a later 1965 bike with alloy forks and low riser handlebars, which is surprisingly comfortable and the bike is better than it looks overall. Gear shifting was a bit cranky sometimes, but it did go into all 4 gears without much effort and the clutch is working great now!

1967 CL77 notes

This bike is an enigma as it only shows less than 1600 miles on the speedometer and is complete and original apart from some tires that were swapped onto it many years ago. The seller swore that it ran great when he had it running, but that was about 5 years ago.  A fresh battery awaits this poor machine, which suffers from a lot of chrome corrosion on the fenders, tail light bracket and fender stays.

Once the battery was installed, the carbs cleaned and new air filters installed, the bike was a good runner, but still looked very sad with extensively corroded chrome plating everywhere on the bike.

September wrap-up

SOLD!  1966 CL77 to a Mid-West enthusiast who already owns and has restored 450 motorcycles! Sale came at the VJMC West Coast Rally in mid-Sept.

SOLD! 1966 CB77 to a local friend in his 60s, who is actually re-learning to ride a motorcycle, after taking the safety classes. He wanted a Super Hawk, but not too good of one to ride around town and have to worry about dropping it and damaging a high-dollar show bike.

SOLD! 1965 CL77 to a buyer who came all the way down from Watsonville, CA! His late arrival on a Sunday conflicted with  my plans to attend the annual DGR ride here in San Diego, which I had to forgo in order to facilitate the sale of the Scrambler.

SOLD! 1969 CL175K0 to a buyer who came down from the Ontario, CA area in a 1977 Toyota PU truck. The little Scrambler gave me fits at the end, having to R&R the engine 3 times to overcome a camchain snagging issue that kept popping the master links apart. It ran well after all the work was completed, but the wide-open throttle stumble left me baffled and I never fully figured out what was happening with it. Sold cheap, so new owner can play with it and sort out whatever was happening, I guess.

Score four and many more to go… Cont.

CL77 notes

Looking like the most promising of the four bikes, the 1966 CL77 showed only 3600 miles on the odometer and the whole chassis had been powdercoated in an earlier restoration effort. The fuel tank was clean and a rebuilt petcock was installed, along with a new battery. The battery was the first challenge to surmount, as the battery terminals on the CL harness have installed nuts on the connectors that are not a match for the posts on the new batteries. Eventually, a Dremel cutoff wheel was used to saw through the outside edges of the battery posts and a little redrilling of the holes allowed the battery hardware to finally connect up. With power ON the horn worked, as did the other electrical components which were still attached. There was power to the ignition system, so from that point the rest would be regular tune-up adjustments…. Or so I thought.

The carburetors had shiny air/speed screws installed indicating carb kit repairs. When the float bowls were dropped down, a thin layer of oil gasoline deposits were found in the bottoms. The main jets holders were removed and the idle jets coaxed out of the carb bodies, which can be difficult on a CL series machine with the exhaust pipes in place. The main jets were poorly stamped, but I was able to make out that they were #130 sizes, which is about right for a 305 Scrambler. The idle jets seemed to be open as I could see light through them, but when I pushed the jet cleaner wire into the jet, it wouldn’t go! I tried going in from both sides, but still no luck. Grabbing a magnifying glass I was able to make out the number 30 barely stamped into the jet faces. WHAT??????  I have NEVER seen a #30 idle jet applied to any Honda motorcycle engine, no matter how small it was. Ah, the joys of aftermarket jet kits!!! I dug out a pair of #38 jets from spares boxes and installed everything back into the awaiting carburetor bodies, still hanging off the back of the cylinder head.

The ignition timing was next and the first thing that was noticed was that the points were ND style but not ND branded parts. I have had bad luck with these parts in the past, as they often don’t allow a good gap and proper timing within the limits of the point plate slots. The gap on the right side was barely perceptible when opening. After contact cleaning, the left side was set to .014” and timing plate adjusted so they just opened at the LF mark. The right side gap was carefully adjusted until they just opened at the F mark AND had a decent point gap setting.

I dropped the fuel tank on the frame, cut some new fuel hoses and went to fill the tank with gasoline. I thought it was ready to receive fuel, but I had overlooked the fact that the fuel tank was a late model replacement tank with NO crossover tube and that the petcock still had the crossover tube fitting in place… open to atmosphere! As I poured gas in it flooded out over the motor until I finally figured out what had happened. With one hand I was able to plug the fitting and with the other hand cut a piece of fuel hose and stick a 6mm screw into the end to make a block-off plug. I slipped it over the petcock fitting and mopped up the fuel overflow on then engine and off the floor. The bike doesn’t have any air filters or connecting tubes so any kind of a back fire would have lit it up into a ball of fire.

I did check compression readings on this engine which were 180 psi on both sides, so this should be a healthy motor. With just a couple of kicks, the engine fired up and smoothed out quickly. With the stock OEM muffler system in place, the bike is relatively quiet, but the whole package is not without its own set of harmonic tones.

I put the seat on loosely, turned the bike down the driveway and pulled in the clutch to engine 1^st gear. I could feel it jerk into gear because the clutch plates were “stuck” from sitting, however with the clutch lever held in and a few engine revs applied the clutch disengaged and worked somewhat normally again. I ran it down the street checking the gearbox and then rolled it back up the driveway to rest for awhile. This one turned out to be better than expected so far. Hopefully, someone will adopt it before more work needed is done by me.

Score four and many more to go…

Just when I was getting a few less bikes in the driveway, my friend Burt forwarded a Craigslist posting that showed many, many Honda motorcycles up for sale. The owner was cutting down his collection of about 100 machines, mostly 1960-70s models. His aim was to focus on SOHC Honda CB750s and he had managed to acquire a rare sandcast CB750, although the engine was stuck when he bought it and the bike was a definite candidate for a full restoration.

The trip to Riverside, CA took about 2 hours, as we went north out of San Diego during the late morning hours. As advertised, the seller had a LOT of bikes, but a fair selection had been left out in the open, covered loosely by tarps. It took awhile to get to know him and see the collection of bikes and parts that were covering steel racks around the edges of his large workshop space. He had 3 bike lifts in place, all supporting various project bikes, including a C110, CB750K0 and something else I don’t recall.

Most all of the bikes were projects and eventually we came to an agreement to purchase four bikes: 1966 CB77, 1966 CL77, 1967 CL77 and a scruffy CL175K0 Scrambler with a stuck engine. The CB77 was pretty complete, but had shorty mufflers attached. There was a set of CB77 mufflers found on a rack, which were included in the deal so that made it more palatable.

Burt had followed me up with his Nissan Frontier pickup, so we were able to put two bikes in his truck and a pair in my 2002 Tacoma. The time spent at the seller’s house, plus a stop for a late lunch put us back on the highway moving into rush hour, so eventually the return trip ran past three hours before the bikes were unloaded.

CL175K0 notes

I brought the 1966 CL77 and the CL175K0 home for immediate care. The little 175 Scrambler was seriously seized and very rusty on most all of the metal surfaces. The bike had Oregon title/plates and looked like it had been sitting in the moist elements of the Pacific NW for many years.  I extracted the engine, pulled the head and coaxed out a seized left side piston, which loosened the cylinder liner in the process. The piston rings were all stuck and/or cracked-broken in the ring lands, but the engine seemed to be in the kind of condition that verified the 3600 miles showing on the speedometer.

The cylinders were still on STD sized bores; so a pair of pistons and rings was acquired from David Silver Spares, along with seals, gaskets and carb kits for the power-jet 20mm Kei’hin still attached to the original, decaying air filters. DSS had a new wiring harness and headlight shell for a reasonable price, so those were put on the order sheet, as well. DSS had one fork ear and another one was found on eBay.

On the bright side, the fuel tank had been cleaned and lined, so that task was already handled. The petcock needed an overhaul, but fortunately the repair parts for these models are plentiful.  A new battery was locally ordered, which is substantial considering the bike does not have an electric starter system to power up.  The muffler had surface rust, especially on the exhaust flanges, but there were no holes underneath the end of the muffler assembly, which is a rare occurrence these days.

My friends at 4into1.com offered some tire/tubes/band sets at a discount, so two sets were ordered, as they fit both the CL175 wheels and the CB77! The forks needed new seals and fork boots, so those were ordered, however the “fits CL175” eBay seals were 31x43x10 vs. the required 31x41x9.1 sizes. I finally just ordered seals from my friendly Honda dealer and got them in a couple of days. 

That all went together okay, however when the front wheel was removed, not only was the drum surfaced rusted over, but one of the brake shoes had NO brake lining in place. Apparently this bike was used as intended (i.e. a Scrambler) and driven through Oregon mud and streams, plus was suffering various oil leaks at seals and gaskets. One supposes that the front wheel was submerged a few times and left to stand as-is. Eventually, the lining on one shoe unglued itself and probably jammed the front brake when the bike was moved, so the wheel was removed and the loose lining removed, and then wheel reinstalled with only one brake shoe working.

Brake shoes were another “fits CL175” issue, when the ones that were supposed to fit were found to be too small and not the cross-match that was indicated. Another confirmed part number shoe pair was found on eBay and they arrived quickly. In the meantime, there was a LOT of rust removal of the brake drum surface and the rest of the brake hardware to do. Both wheels needed to be de-rusted and deglazed to allow proper function once again. The brake cams were locked in place, but judicious use of some penetrating oils and a soft hammer got them freed up so they could be cleaned, lubed and reinstalled. 

The new Michelin tires were installed on both wheels giving it a more modern look.

DSS came up with a nice reproduction speedometer cushion, which happens to be the same as the one used on the CB450K0 Black Bomber. New cables were procured and slowly the bike regained some form of motorcycle look and function. The chassis was cleaned with S100 and scrubbed up a bit so that some anti-rust treatment could be applied followed by most of a can of Duplicolor Gloss Black spray paint.

Rebuilding the top end of the engine was risky, in that the cylinder bores were somewhat roughed up from the seizures and the intake valves had typical cupped wear at the seat edges. The valve seats in the head were somewhat rough condition and one had a deep rust spot right in the valve seating area, which required more and more cutting and narrowing of the seat until the corrosion pitting was erased. The intake seats were touched up slightly and the new contact area was very narrow and problematic.

After several rounds of scraping, chemical cleaning and scrubbing, the engine assembly was finally installed with a bit of patina intact. After working out all the wiring connections and setting up the ignition timing, the engine was finally fired up for the first time in many years. Once the bike was running, I listened and watched for signs of distress of any kind. There was smoke out the muffler, but a lot of that was due to the old buildups inside the pipes and muffler that needed to burn off as the engine came up to temperature.

The engine took throttle crisply but didn’t want to idle down without dying. Ignition timing was rechecked and the left carb removed for another look as it only ran decently with the idle screw backed out about 3-4 turns vs. the correct 1 to 1.5 turns from the factory tune up manual info.  I rechecked the valve clearances to make sure that one of them hadn’t sunk into the seat but all seemed okay there. Finally, I ran a compression test and found 120psi on the right side and only 90 psi on the left. I hoped that running the bike in for a few miles might help seat the rings and the valves more forcefully and bring up the compression readings. The bike felt quite crisp under power in all gears and I enjoyed my 3-4 mile local test run, but on the return the engine continued to quit when allowed to idle again. Follow-up compression readings verified that nothing had changed from the earlier readings.

New intake valves were ordered and will have to be installed when the engine is dropped down for inspection and repairs. I did notice a good bit of oil coming out of the breather tube after the test ride, indicating that the piston rings were still not bedded in yet, however the spark plugs came out nice and dry on the tips, so it wasn’t pumping oil into the combustion chambers. There was no visible smoke out the muffler either, which was a good sign. Unfortunately, the right side spark plug hole threads are somewhat damaged and will probably require an insert to shore up the thread hole. This can all be done when the head is removed for new valves. This is the kind of experience to expect sometimes when you are in a hurry to get a job done and get onto the next stage of the project and/or other projects that are backed up currently.

Reflex Reflux – a Space Odyssey through the Van Honda belt system

This somewhat sad and frustrating story began several months ago…  My friend Burt called for help with his 2007 Honda Reflex 250cc Scooter, which had suddenly died on the highway and wouldn’t restart. I jumped in the Tacoma and found myself within 100 yards of the Mexican border where Burt was waiting with his stricken scooter. We loaded it up and hauled it back to the Santee area shop where it was left for diagnosis and repairs.

Burt checked for fuel and spark and compression, all of which were present in what seemed to be stock specifications, however the engine would try to start up initially and then just die for no clear reason. Restart and repeat, over and over again until the battery gave up the ghost. Burt bought a nice new battery for it, tried the restart and was met with the same results. He called me for some advice and I ran through the normal checklist of what was needed and what he had found. There were no clear clues so the troubleshooting became more and more esoteric and all kinds of possibilities discussed. Burt replaced the ignition module and the starter valve, but time after time, no improvements could be made. The carburetor came off for cleaning and inspection. Apart from what appeared to be a slightly plugged idle jet, nothing else seemed amiss. Stripping the bodywork off of these scooters in order to access the engine and fuel system is rather arduous and time-consuming, but wound up being repeated any number of times as different “cures” were tried and found to be lacking in positive results.

Burt had other bikes and projects going on in his life, but this Reflex become a source for “Reflux” as his mind churned over and over again about what to do, why it hadn’t responded to various repairs and the overall spirit of feeling a sense of defeated by mysterious mechanical ailments yet to be uncovered. Finally, in a desperate plea to me for hands-on help, so I agreed to take on the unruly 

Reflex to see if I could make any headway with it for him.

With the bodywork removed, I checked the compression which clocked in at 230 psi, right on the money. There was a nice steady spark at the plug, but when we tried to start the engine, it coughed and sputtered and then died quickly. The sound, to my ears, was that of an engine that was flooded/way too rich running. Removing the spark plug again, the cylinder spewed out a stream of raw gasoline which luckily didn’t ignite off of the nearby spark plug hanging on the plug wire. I drained the carburetor bowl and started pulling vacuum lines off the carb and intake which control various components of the emission control systems. When I pulled a line off of the top of the carburetor body and cranked the engine over MORE raw gasoline flew out of the uncorked port.  What the @#$%!% is going on here?

Obviously, the carb had to come off for inspection. It is buried down in the frame, but removing the manifold bolts and throttle cables allowed it to be worked free for bowl removal. What I noticed was that the float bowls do NOT have an overflow tube or way to shed excess fuel if the float valve sticks open. I removed the float pivot pin and float to check the tip of the needle. I happened to have a spare new needle on hand, but it didn’t make sense that the needle was really a problem. What WAS the problem was a tiny sliver of shaved off fuel line or an edge of an o-ring that was nestled down deep in the float valve seat! At first it looked like a bit of dirt or fuel varnish, but when I probed it with a scribe tip, it moved around the bottom of the seat. I dragged it out of the recess and looked at it carefully. Sure enough it was rubber something and it was just big enough to have blocked the float valve from closing all the way. The fuel pump kept pumping gas into the bowl which then was being sucked out of the carburetor bowl vent fitting. An errant placement of one of the vacuum lines on that vent fitting had intake manifold vacuum sucking fuel out of the bowl and back into the intake manifold as raw gasoline!  No wonder it was choking and sputtering when we tried to start it up!

I was getting more confident that some substantial progress was happening now and after the spark plug was replaced in the head, the engine fired up immediately sounding strong and showing no signs of stalling out. While I was revving the engine to clean out the cylinder from all the raw gasoline inside, Burt noticed that the rear wheel wasn’t moving at all!  Honda belt-drive scooters use variable pulleys to adjust engine load and vehicle speed. The wheel should start moving immediately as the throttle is applied from a stop. This one did NOTHING! Big clue… the original breakdown failure on the freeway was a broken belt! The belt fragments wrapped around the crankshaft pulley and kept grabbing the engine as it began to run. The engine and all systems were probably just fine when the belt broke, but you can’t see the belt inside the belt case and the “symptoms” were that the engine didn’t want to start and run. Normally, those symptoms are related to lack of fuel or some kind of CDI breakdown or other component failures. In this case, the engine systems were okay, but the belt drag was keeping it from operating again.

Burt wrapped up the bodywork and we loaded the scooter back into his Nissan pickup. He reported that the belt was mostly fragments, with maybe 1/3 of the length still intact. Once he finds a new belt, the bike should be good to go, once again. Finally, the sleepless nights and acid reflux symptoms are subsiding for Burt and the bike will be going up for sale, as soon as he completes the final repairs. It was a long and frustrating challenge for Burt and his various advisors. Before he brought the scooter to me, he had taken it to two repair shops for diagnosis and they sent him off with no further insights as to what the problem might be, apart from observing that the scooter needed tires and a right fork seal!

So, after a couple months of trial and error, the Reflex Reflux case is now finally concluded and it will again be able to fly through the Van Honda Belt with speed and efficiency as designed.

Busy, funny, scary news updates…

I haven’t been very consistent in my blog postings lately, due to a number of situations that have arose over the past month…. But I’m BACK now.

Let’s see… There was the matter of the CL125A, which needed some attention for oil leaks, fresh rubber and some performance/appearance issues. The shift shaft seal was replaced, new fork boots and one fork seal were replaced, new tires/tubes installed and the muffler was welded up on the inside where a hole was rubbed through from contact with the shock absorber. A new battery was procured, of course, and the fuel system cleaned and re-jetted for modern fuels. It was too underpowered to make the hill nearby which leads to the post office, so the bike was offered up for sale and found a new home in Ventura, CA as a result of an eBay auction. The buyer had one just like it when he was a kid! That will sell a bike every time, when you find that right buyer.

Busy, busy

While that one was pending sale, a 1982 Honda FT500 Ascot showed up in running condition, but needing some TLC in the usual places that these bikes require. The air box was cut in half, which allows a large K&N air filter to be used in conjunction with some adapters to allow use of the crankcase breather system. The bike has a custom-made rear luggage rack that even included little LEDs in the back end of the rack rails. The owner worked at a metal fabrication shop and thoughtfully created a sturdy rack for his lunch box, while commuting to work. The seat cover was original and splitting apart, so a nice aftermarket replacement cover was procured and installed with the help of an upholstery shop. My staple gun didn’t have enough power to put staples into a plastic seat base. Fortunately, the seat foam was still intact, so a cover was all it needed to make it attractive again.

After some trial runs, it seemed that the carb jetting was a little off. The spark plug looked pretty good, but there was a flat-spot off the bottom into mid-range that was annoying. All the testing revealed an oil leak at the camshaft rocker arm cover, which was an ongoing problem with those bikes and the related XL500s back then. I ordered a gasket kit (EMGO) but the head gasket was less than stellar. A couple of the bolt holes were off by half a hole. That necessitated some gasket mods to get it to go together again. The camshaft lobes were somewhat pitted, but not necessarily from lack of lubrication. This seems to be another problem area for these bikes, perhaps due to insufficient surface hardening. When the rocker cover was removed, it was evident that someone had been in there before, as a number of bolt holes had inserts installed to repair stripped out threads. Again, this is another long-standing problem with these bikes.

The balancer shaft adjustment can only be made by removing the clutch cover. The spring-loaded tensioner arm moved a couple of notches before coming to a stop. Honda recommends backing off the tensioner one notch from where it stops.

When the carburetor was removed for inspection and jetting, it appeared that the slide piston was somehow jamming up into the top cover, so the throttle never really fully opened to full power. A friend had some CX500-650 used carburetors, which share the same components as the FT500s, so that fixed that problem. Eventually, I would up with a #150 main jet, the CX500 needle with shims and a larger idle jet to finally solve the performance issues.

The bike came with bar-end mirrors, so I wound up spending over $100 for a set of OEM mirrors, which are just about gone from anyone’s stock now. After a test ride, the right front turn signal lens promptly broke off and fell into the street as I came up the driveway. A pair of OEM lenses was found on eBay for $15 including shipping, so now I have a spare, just in case this happens again. I have never seen that happen before! It was like something out of a comedy show… ride, ride, clink, clink…. Stop and recover the lens from the driveway. All the other three seem to be just fine.

The electric starter systems on these bikes are somewhat problematical so the covers were removed and the system inspected, cleaned and serviced. So far, it is working well now. The FT500 is up for sale now, as I continue to try to trim down the motorcycle herd nestled in the driveway.

Funny/sad

The last three people who reported hard starting problems had bikes with battery levels that were WAY TOO LOW to allow the battery to charge up and stay charged. These lead-acid batteries need regular checking at least once a month.

Sad/scary

Finally, a long-time customer rang me up to ask about redoing the top end on his CT90K1 Trail 90. In general, parts have been available from Honda and the aftermarket for many years. Honda must have build a couple of million of the OHC 90-110cc horizontal singles since their 1965 introduction. Honda placed those engines into ST90, S90, SL90, CT90, ATC90s and many, many more.

Taking the top end off is about 15 minutes work, even with hand tools, so the autopsy can be done quickly when there are problems. The bike was using smoking and using oil since the last visit, so the focus went to the piston/rings/cylinder bore primarily. Despite a smooth-looking bore, when the top compression ring was removed and fitted to the ends of the bore, the bottom measured out at .008” while the top measurement was out about .020”+, so obviously there was a taper in the cylinder bore.

The bike only showed about 4400 miles on the odometer, but the overall condition was fair-average. The bike has been used as designed, out in the sand, gravel and general off-road conditions. When the piston was extracted, the first thing noticed was a loose-fitting piston pin clip, consistent with those found in a lot of Chinese-made piston kits. The piston was marked 028 (product code for an S90), but it had a 3 piece oil-ring, which the bike never came with from the factory. I wondered why a low-miles bike would have a replacement piston until I removed the carburetor and discovered that the little choke flap was missing from the choke plate! It was another case of flap failure, which I have seen on many of these kinds of carburetors made in the 1960-70s. The spring loaded flap fails and gets sucked into the engine, where it usually jams the intake valve open long enough to have the piston come up and bend it smartly. The valves in the head were cupped at the seats, so new valves were ordered and fresh valve seats cut in and the head assembled for final work.

There wasn’t any sign of catastrophes inside the combustion chamber, but the head could have been changed when the piston was damaged along with the valve. There were a few Heli-coils in the threaded holes, so obviously someone had been inside the engine at least once before it came my way. When I started looking for an over-sized piston, I discovered that Honda has discontinued the S90 series pistons and ring sets from US inventories! It is one of those things that will last forever, but I see that this isn’t the case now in the 21^st century. I was able to find one set of OEM rings at a Honda dealer up in Orange County, plus one matching OEM piston from an eBay seller in Texas. I tracked down a pair of 14mm wrist pin clips after going to two different dealerships….. ?!?!? It really is shocking that you cannot find wrist pin clips in stock at a motorcycle dealership these days. The first local dealer didn’t stock them and the second one, some 12 miles away only had two available. I guess people are not rebuilding their bikes much anymore….  Sad isn’t it?

I did find that the camchain was pretty well stretched, so a new chain and guide roller were ordered up, along with a quality Vesrah-branded gasket set. These engines have a valve stem seal on the exhaust valve side, which was replaced with a spare that was in stock, but it was surprising that the complete gasket set didn’t have this tiny part included.

Two 25-mile round trips later to drop-off and pick-up the newly bored cylinder yielded a nice smooth, straight and round cylinder to fit a new piston into, now at factory specs. As fast as it is to tear down one of these engines, the reassembly/repairs take several hours. The valve job probably took about 45 minutes as the seat contacts were adjusted several times until they centered on the valve head. Scraping gaskets, checking threaded holes, replacing seals, doing a valve job, cleaning parts and carefully reassembling this little engine takes a lot of patience and some expertise.

With the carburetor cleaned out, float adjusted and some new gaskets/seals installed the engine finally was ready to run, once again. The engine fired up after a few kicks and once the oil solids coating the inside of the exhaust system burned off, the engines ran smoothly, with little noise or smoke evident now. It will probably receive a slow break-in period at the hands of the owner who has enjoyed it, even as it was, for many years.

The CT90s have a dual activated rear brake, which also incorporates the brake light switch. If either of the rear brake functions jams up, the brake light will stay ON and eventually run the battery down because the little 6v system is barely up to the task of keeping a fully-charged battery up to normal voltage levels. This bike was a 1969 CT90K1 which had a front brake light switch function as part of the brake cable. The cable was changed to a non-switch version, so loose wires are flying in the wind at the front fork area. Honda made many changes to these bikes through the years, so keeping them stock with OEM parts is a challenge now. 

I think that brings us up to date so far… MrHonda

Coming through in the clutch… Honda 250-305 clutch history

One of the most confusing aspects of 250-305 engine repair is sorting out the numerous versions of the clutch assembly. I will attempt to demystify it here, if possible.

Honda began the new wet-sump engine series in 1960, starting with the 250cc Dream, then adding the 305cc version soon afterwards. In 1961 the CB72 and CB77 Super Hawks emerged from the factory, followed by the new 1962 CL72 250cc Scramblers.

Honda started with a light pull, conservatively-designed 4 plate clutch used in the first generation C/CA72 250cc Dreams.  In the parts books, you will see these parts with 259 part codes, which is the code for the 250cc Dream engine series. With the somewhat higher power output of the 305cc engines, the parts were upgraded to 266 codes for the clutch pack and the primary chains. Yes, there were three different parts numbers just for the primary chains, starting with 259, then 266 and finally the 268 code part for the CB72.

The thick 5mm friction discs of the 250s, coupled with very light clutch pressure springs resulted in clutch wear and failures fairly early on in the production cycles.

From the 1960 Dream parts books we see:

The 250s had four thick friction plates and four steel plates. The center hub had no grooves for retainer springs. Early pressure plates have been seen with small metal pegs inserted around the edges with tiny coil springs attached, which helped push the clutch assembly apart during disengagement. The 305s had five sets of thinner plates. One set of clutch springs sufficed for both versions, at first. Apparently clutch wear and failures became common, so a new set of clutch parts were designed for the Dream engine applications. Notice there are two clutch outer part numbers. The first is a solid mount rear chain sprocket style and the 010 version was the improved “cush drive” model. The inner clutch hubs came in two more types using the stopper rings, fitted into grooves machined into the clutch hub. Ring groove locations varied due to the differences in the thicknesses of clutch plate pairs which were being retained by the stopper rings. 

Clutch springs were offered in 259-000, 259-010, 266-000 versions, which became progressively stronger, as necessary. Clutch centers were offered in 259-000, 259-020, 266-020 and 266-030 for 250 and 305 models, respectively. The early model clutch friction plates were molded solid fiber material. As the clutch designs progressed, the 268-020 coded friction plates were made in aluminum-backed parts with the friction material bonded to the metal backing. Friction materials varied in thicknesses depending upon the application and number of plates used. Dreams wound up with either 5mm thick, 4-plate clutch packs or the thinner 4mm 5-plate combinations. The Plate “A” (first plate on the hub) was generally 2x the thickness of the other steel plates. Steel plates come in several thicknesses, so just the right combination of parts needs to be achieved to create the best possible clutch pack build.

What is important to remember is that no matter what combination of friction and steel plates were used to complete the clutch pack, they ALL had to have the same stack height when installed on the engine. If the stack height isn’t matching to OEM specifications, then the clutch release components inside the right side kickstarter covers will not have the correct geometry to effectively release the clutch pack when the clutch lever is pulled in. The clutch lifter arm must travel through a shallow arc, starting below horizontal plane and arcing upwards above horizontal. As the clutch lifter arm moves within the clutch adjuster (fixed in the kickstarter cover), the coarse threads of the two parts create a pushing motion on the end of the clutch release pushrod, which contacts the big ball bearing nestled deep inside the clutch lifter arm.

Many people have discovered sudden loss of clutch lever action, usually when the kickstarter covers have been removed for servicing or clutch cable replacement, due to the ball bearing dropping out of the lifter arm hole. The thickness of the ball takes up considerable amount of lateral play in the clutch release mechanism, so when it is missing it is impossible to adjust the clutch free-play using the cable adjusters or the clutch adjuster on the side of the kickstarter cover.

Scrolling down these pages to the CB72-77 clutch parts list, you will see that there was a 6 plate clutch offered, a 5-plate version using all fiber friction plates and finally the last generation 5-plate clutch using the metal-backed friction plates. Obviously, in order to accommodate a 6 plate clutch pack, all the plates needed to be thinner than the 5-plate set. The last generation CB72-77 (and CL77) used a clutch center with retainer grooves placed to allow the thicker plates to be installed and retained. The last of the steel plates had anti-warp notches stamped along the inside edges to help keep the plates flat when they became heated during aggressive operation. The Plate A is quite thick and has a beveled back edge to clear the clutch outer when installed. Late version pressure plates have angled drain holes to help evacuate trapped oil inside the clutch assembly.

There were three different clutch covers first due to a change in the shift shaft lengths, then the progression from “small hole” to “large hole” outer oil filter cover sizes. Remember to check your new parts against the old ones, when doing replacement of components.

CB72-77 clutch springs went through a series of part number changes from 268-000 for the 250s, followed by 275-000/010 for the 305s, then to the very stout 275-810 racing clutch spring. For most normal stock street applications, the 275-000 spring (equivalent to the 323-003 CB500 Four spring) works fine with stock clutch pack parts. These springs give a nice balance between light lever pull and sufficient pressure to prevent clutch slippage. Use of the later 275-810 springs will give the rider a very heavy lever pull experience, but does ensure that clutch slippage is pretty much non-existent.

When there is wear inside the clutch adjuster threads, there is a progressively lessened amount of clutch pushrod travel to disengage the clutch plates. The wear increases the amount of force needed to disengage the clutch to the point where the combination of heavy springs and worn clutch release parts can cause damage to the early version kickstarter covers. Later versions of the kickstarter covers were designed to move the clutch cable joints more forward, closer to the cover retainer screw mount.  Increased strengthening ribs were incorporated into the cover design to help prevent breakage which is especially common in the Super Hawks, which have forward-kicking kickstarter levers.

Well-lubricated clutch adjusters with minimal thread wear will enhance clutch lever pull efforts in a positive way. Heavy clutch lever pull effort is often a combination of dry and worn (and misrouted) clutch cables, worn clutch lever pivot bolts/holes and excessive clutch adjuster thread wear.

CA clutch parts list (1969 book):

                                                CB kickstarter cover... ready to install.

Final conclusions:

You cannot indiscriminately mix and match Honda friction and steel clutch plates and have a normal operating clutch on a 250-305. Steel and friction plates come in various thicknesses and designs.

You MUST use the clutch plate pack that matches the inner clutch hub retainer wire grooves AND use the retainer wires, as designed. These “stopper” wires are becoming extinct, so I have used picture hanger wire or very thin safety wire to use for the same function. Installation of the plain wire requires drilling an additional hole in the hub and securing both ends of the wire inside the hub where the stopper wire ends usually wind up after installation. If you leave the stopper springs out, you will have difficulty in selecting neutral when the engine is running and you are at a stop light/sign and need to release the clutch in neutral while you wait.

The best solution is to use the 1965-ish and later CB/CL77 clutch assembly, which includes the cush-drive clutch outer and the sturdy 268-020 friction plate sets. See photo below for comparisons to your clutch assembly. Remember if the clutch pack stack height is not correct, clutch engagement/disengagement issues will arise.

Using a CB/CL77 clutch is perfectly fine in a 250-305 Dream. You might play with using some of the lighter clutch springs to lighten the clutch lever pull, as strong springs are not needed for Dream applications. The Honda 425 code springs are the superseded parts for the Dream clutch springs.

Using Barnett clutch kits will not allow use of the inner hub stopper springs, so clutch release at a stop sign/signal light will be compromised. Barnett plates tend to drag when cold and the spacer plate they use to compensate for the changes in plate thicknesses will cause problems for street use. IF you are racing your bike and don’t care about street use, then going for heavy springs and heavy duty clutch plates may be the way to go, but you will have difficulty getting the transmission into neutral without the stopper springs in place.

Watch out for late model “shallow spline” replacement parts, used on 1966-67 models. You can use the shallow spline hub, crankshaft sprocket and countershaft sprocket on earlier bikes, but not the other way around. The OD on the shallow spline parts are the same as the deep splined parts, so it is the ID which causes conflicts when trying to use early parts on late shafts.

 Honda has superseded the 259/268 steel plates to 329 code parts from the XL350.