MrHonda and the Little Bike of Horrors, Part 2

 Yeah, this is overly long and probably should have been cut into thirds. It took a couple of hours to put together 7 pages of story on just one bike. Indulge me.... 

Installing a new MOTOBATT battery in the frame, gives power to the electrical system, allowing to check all the lights, power to the coils and points, horn function and starter button. Changing from the high bars to “flat bars” brings up more issues with feeding wires through the handlebars and what always seems to be an issue with the little starter button wire in the switch. The insulation shrinks back and the bare wire contacts the hold down plate, causing instant starter function as soon as you turn the ignition switch ON. I had to remove the switch wiring and attempt a soldering repair on the shortened wire. I couldn’t quite get the wire soldered in place to allow the wire insulation to miss the bracket. Finally, I dug out some old handlebar switches and found one with an intact horn button contact plate. This required pulling the little black, instead of yellow/red tracer wire through the bars and installed into the switch housing. All these little repair functions eat repair time in amazing amounts.

Finding “flat bar” cable sets is becoming more and more difficult. I ordered a full set from Thailand and they all worked except for the throttle cable which was about 4’ too long. All the replacement cables coming from Asia have plastic junctions instead of the OEM metal types and the cable sheaths all flop around loosely when you are trying to install the ends. I put a drop of GOOP on the cable joint where the splitter attaches the two leads to the carb tops. That helps stabilize the twin leads to the carburetors.

The carbs were cleaned in my little ultrasonic cleaner and basically all parts reused apart from new float bowl gaskets. When the bowl was dropped out of the left side carb initially, someone had tried to stuff a square bowl gasket inside the round bowl body and bowl. These kinds of discoveries show the lack of level of care or knowledge of repairing these old bikes.

The headlight had been removed, to replace the road rash damage on the rim. While in there, it is always worth a look at the neutral light boot and light socket connection. The boots get hardened with age and heat. The bulbs that fit correctly have to come from Honda, otherwise aftermarket bulbs don’t quite fit inside the boot and allow connection to the lens unit in the headlight shell. This bulb socket had been held together with masking tape, which had hardened and fell apart. New reproduction boots are available from www.classichondarestoration.com for little money. I always have to replace them on any bikes that come my way. After installing a new boot and peeling off the masking tape from the bulb socket, I mated them together and checked for continuity with the ignition switch turned ON. I had power on both sides of the bulb, so the bulb was okay, but the path to ground was not complete. That means that probably the neutral switch wire connection has failed, assuming the the wire is connected properly to the stator wiring harness. 

Oh, the stator was trashed with all the coil insulation peeled away, so I was able to drag out a good used one from stock but the harness plastic sheathing was all cracked and hardened. So, MORE TIME was spent on cutting of the old sheathing and replacing it with some heat shrink tubing. I had to cut a slot in the tubing to run the neutral wire through and into the bundle of connectors in the wiring harness. So far, so good, BUT there was still no connection to ground through the neutral switch when the transmission was in the neutral position. This, invariably, requires removal of the switch from the inside of the cases (remove the kickstarter cover again) and check the switch for the usual broken solder connection at the switch face. Despite looking secure when first installed, there is a little tab that holds the wire in place, disguising the fact that the solder connection at the end of the wire has failed. Pulling the little tab loose from the switch body, revealed the separated connection.

                                                                   Looks good, but isn't....

Repairing the switch is usually fairly easy with a soldering gun and some solder. Cut back the wire end about an eight of an inch, then tin the wire end with solder. Clean the little round connector point on the switch and heat them both together very quickly. If you overheat the connection, the contact button on the inside of the switch plate will distort and the inside switch ring with a single high point to connect with the plate contact will be swollen up and won’t make contact even when the wire is repaired and the switch ring is in the correct position. This requires prying back the little crimped ears on the switch backing plate to remove the contact plate to flatten it all out again, so the internal contacts are again regained.

                                                            Dab of solder and it's back in business.

Finally, I get the neutral light to illuminate with the headlight still removed. The neutral light boot connection to the socket is rather fragile and when I put the headlight and wiring back into the shell and secured the rim screws, the neutral light quit again. Removing the headlight again showed that the neutral light connection was pushed off the lens fitting and it was lying back inside the headlight shell. Careful positioning of the headlight wiring and the neutral light socket connection finally gives joy to the repair.

After checking the ignition timing statically, I noticed that the point backing plate was moved all the way to the end of the slot in order to get both sets of points to fire at the F and LF marks. This indicates that either the point rubbing blocks are worn down or the points were replaced with non-OEM point sets which have incorrect geometry. If the point backing plate is stamped ND (Nippon Denso), the points also need to have the little ND mark on the base. Installing a replacement electronic ignition does away with these challenges, once the system is adjusted properly. Something that has come to mind is that on a new engine with new seals, the seal friction on the point cam where it pokes through the cylinder head cover can cause a delay in the point cam returning to rest at idle. Heat and miles will tend to relax the seal lip friction and the timing should return more easily, allowing the engine to return to idle more quickly.

FINALLY, it was time to light it up and see what the results of many hours of work produce. Suprisingly, the engine fired up on the second revolution with full choke applied. It coughed and spit back for a few minutes, then settled down somewhat with carb screw adjustments. Typically, the idle screws need to be out about 1 turn from gently seated. This setting can vary depending on any issues with air leaks, fouled spark plugs, idle jets not correctly sized and warped carb flanges, plus flattened out o-rings on the flange and insulators. I have found insulators with blown out o-ring grooves, which are not noticeable from the top. These lead to massive air leaks at the head.

I ran the bike off of my remote fuel bowl to allow me to check carb synch, any signs of spit-back and general operational problems. I ran it for a few minutes, stepped away after shutting it down and discovered a small pool of oil running of the right side exhaust pipes. The cylinder head covers often leak if the surfaces are not dead perfect flat. I added a second gasket to the parts, which mended the leaking problem. I restarted it and checked for more leaks and found none. As the engine warmed up I noticed some oil-burning smoke coming from the mufflers. This can often happen when the exhaust system has leftover coatings of oil and un-burned fuel deposits that flare off when the engine exhaust system is coming up to operating temperature. Often this continues for about 15-20 minutes when just running it at idle in neutral. Pulling the spark plugs showed a bit of oil burning on the left and a bit more on the right side which was the cylinder with more piston clearance and a bit of scoring below upper combustion ring travel.

The next step was to refit the fuel tank, but only after rebuilding the petcock. The repair kits are inexpensive from 4into1.com and www.classichondarestoration.com Once the corrosion and old fuel deposits are cleaned from the bowl and all of the fuel line fittings, the kit goes in easily. BUT there is often a problem with the back side of the petcock lever face. Years of being left in one position or the other allows fuel acids to etch into the face of the lever, causing them to short-circuit the normal function and start to leak past the lever and/or not shut off the fuel to the carburetors in the OFF position. I have a number of used petcocks and parts, but almost all of the levers were etched to the point where flattening them up with a large single cut file doesn’t remove the deep etched divots. I have started to imagine that perhaps a thin layer of JB-Weld smoothed into the surface defects then filed down after the epoxy sets up might save a few of these hard to find parts. The fuel lever fits all the CB/CL 250-305 petcocks, plus other applications like CB350F, CB160, CB500-550, CB750, MT250K0 and apparently a total of 72 different models according to CMSNL.COM. From looking at eBay listings, it is probably cheaper to buy a whole petcock from the list and use the lever out of it. Current lever listings are in the $50-60 each.

The tank, of course, had it’s own problems. It appeared to have been coated with some thin product, but the crossover tube was blocked. I tried to shove a thin wire brush down the hole, but it stopped at the bend. When I looked down inside the filler hole, I could see that there were the remains of a piece of probably 18 gauge wire stuck in place with the sealer. It was too deep to grab with my various pliers, so I stuck a screwdriver down and pushed it around until it broke off. I tried to drill down into the hole with a very long drill bit, but it didn’t have a good angle on the entry point and didn’t go in very far, so it gets left alone. I put an extra long crossover fuel line on it so I can loop it over the frame instead of underneath where it makes a mess when the line is disconnected with fuel in the tank.

So, with the tank and seat in place, I tried to do a test drive around the block. The clutch lever pull was heavy and changed when you changed the angle of the handelbars. When clutch cables get routed with too many turns, the cable binds up inside and the lever pull is increased. As mentioned before… way before.. The first ride out yielded a slipping clutch and some gear change problems. I nursed the bike back home and leaned it against my Tacoma’s tailgate so lessening the oil loss when the clutch cover was removed. That’s when I discovered the Barnett plates were sticking together and that the new set of plates had the correct thickness to allow the clutch lifter and adjuster to resume correct orientation. The clutch didn’t slip on the way back up my test hill and neutral was easier. Checking the spark plugs, they colored up to a nice tan and exhaust smoke had ceased. It will take some time for the new rings to find a home in the cylinder bores and seat in for better cylinder sealing. It needs to be driven more, but the bike has no license plate. I skated by a CHP car parked down the street and pulled up next to a Sheriff’s car at a stop light without being noticed. I had to transfer my newly registered CB400F plate temporarily to let me get the bike out on the road for more testing. So far.... so good. I love putting bikes and parts back into circulation.

Bill Silver aka MrHonda

www.vintagehonda.com

MrHonda and the Little Bike of Horrors, Part 1

 Well, it just never ends… My friend Mario, an avid vintage Honda collector, brought a 1964 CB77 to me to “get running” and change the tires to a more correct size. Usually, this is not a big problem, but when I was in the process of changing out the big, tall OEM Honda bars (probably CB350-450), I pulled the clutch lever and it felt stiff. The bike had been sitting for many years, so I assumed a “stuck clutch” condition when I removed the clutch cover.

I had an inkling of something being wrong when I removed the tappet covers to check the valve clearances and the inside of the tappet covers were coated in a dark, brown-ish coating that didn’t just wipe off with a rag. Even so, it was shocking to see the entire inside of the engine covered in the same brown coating, that looked like burned oil or perhaps that gasoline had contaminated the oil and it sat like that for many years. Obviously, the next step was to pull the engine and take it apart.

Unlike a Scrambler, the engine comes out of a Super Hawk in about 20 minutes. It just drops down out of the frame and onto the work bench. The oil had been drained out before the clutch cover was removed and it looked pretty dark like it hadn’t been changed in decades. I hoisted the engine up on my work bench and began to tackle the disassembly. Once the clutch side parts were all removed and the starter motor pulled off the front of the engine, I anchored the engine on the bench and removed the top cover. There were signs that the engine had been worked on previously and reassembled a bit incorrectly with some bolts and nuts in the wrong locations. The oil seal for the starter clutch had been installed backwards. Additionally, I noted that the right side carburetor was a 1967 specific square bowl replacement and paired to the original left side round bowl carb, which had an aluminum slide needle commonly used in the early days.

With the top cylinder head cover removed, the camsprocket and point cam were in better than average condition. The bike’s speedometer showed about 11k miles and overall it seemed to be about right for the year. One cool factor was it was still fitted with the OEM stainless steel mufflers, although the left side was a bit flattened out from low-speed crash. Apart from the bobbed front fender, the rest of the bike was pretty much as you would expect a 1964 CB77 to be.

The camchain had a link, so that was removed and the chain dropped down inside the engine for the moment. Once the cylinder head was removed, the whole valve train was coated in the brown gunk. The cylinders were lifted off and when the top right side piston ring was removed for end gap checking in the bore, the ring turned out to be a crescent shape due to wear. The end gap was about 1/8” instead of something in the. .010” range. I had a new STD ring and put it in the bore. The ring gap closed down to the .020” range. The cylinder bores were still on 60mm size. Once the top end was removed, the engine was flipped over to access the oil pump and then to split the cases.

The crankshaft throws were all coated in brown, with the connecting rods covered in a fluffy, flaky oil residue. Surprisingly the wrist pin holes were still pretty tight when the pins were inserted. The transmission shafts were removed for cleaning and to check the condition of the low gear bushing and the gear dog overlap. The cases showed the original greenish sealer from the factory, so it was obvious that the bottom end was never disturbed. I did discover a camsprocket return spring and the tiny bit of the anchor that held it in place. This was sitting inside the crankcases. Fortunately, the oil pump screen would have kept it out of the pump, but as the parts were breaking off from the camshaft sprocket, they could have landed into the camchain causing catastrophic damage.

I tried putting the clutch hub in a tub of paint thinner/mineral spirits to see if the brown would loosen, but there was no sign of it softening the coating. All I could do was to call my buddy Brian at his “Small Engine Repair Service” shop and ask if he could fire up his hot tank blast cabinet to see if that would melt off this grimy gunk. He agreed to have me come down on a Friday afternoon to give it a try. We loaded all the biggest parts into the cabinet and he set the timer for 20 minutes. The temperature is 240 degrees and he throws a bit of cleaner into the 50 gallons of water to help cut the crud. After the first go-round, the parts came out looking very shiny! We had to reload the parts into a big basket so they could be blasted once again, especially on the areas that hadn’t been touched by the nozzles. One last round of heated steam even got much of the crankshaft crud removed. We sprayed it with WD40 after it was removed to keep the bearings from rusting up. The bigger questions is going to be if the oil feed passages inside the crankshaft are totally blocked, which happens even in the best of conditions and maintenance. Scrambler expert, Tim Miller, in TX has pulled NOS crankshafts apart and found the factory lubrication has congealed inside the crankshaft throws. UK crankshaft expert Graham Curtis routinely rebuilds pressed together crankshafts of most 1960s Honda twins and find that the oiling passages are always blocked which creates a lack of lubrication for the small end of the rods and elsewhere.

Brian honed the cylinders and measured the bores and the pistons coming to the conclusion that one piston would wind up with a.. .005’ clearance which is well out of spec for these engines. He felt that the bores were good so suggested finding some STD pistons and rings to freshen up the engine’s compression. I gathered up the engine bits and drove them home to ponder what was going to be needed next. Checking eBay sellers, the STD pistons were being offered for silly $80-100 each! I mean really? How many engines are going to be rebuilt with standard bore pistons and rings? I finally sifted through the listings and found a seller with a pair of slightly used STD pistons and rings for $30!

In the meantime, the inside of the clutch cover showed signs of the primary chain touching it during operation. And the poor little oil filter drive chain was so sloppy that I was surprised that it hasn’t jumped off the sprockets. Back at eBay, the “going rate” for both the big 56 link primary chain and the tiny #25 pitch oil filter chains were $150 each! Choosing the Cappellini oil filter conversion, also at $150, does away with the oil filter and chain, using inexpensive Suzuki cartridge filters to screen out the contaminates. A OEM NOS primary chain was listed with a seller in TX , so Mario ordered that one for me. The original oil filter was, as you can imagine, caked with dirt and debris.

In the meantime, the cases and engine external parts were shipped off to my friend John, who lives about 8 miles away. He has a full-on blast cabinet dedicated to vapor blasting alloy parts, once they have been degreased. I dropped them off on Sunday afternoon and they were ready on Monday. This will give the engine external surfaces a nice shiny look, but the real work will be to chip off the OEM asbestos base gasket from the cases, which is exceedingly tedious. It can easily take an hour to get the gasket material off the alloy surfaces. Single-edge razor blades, gasket scrapers and a tungsten scraper were all employed in the removal process. Ultimately, more than 2 hours were spent in asbestos gasket removal from the crankcases, cylinder head top cover and breather plate and one side of the cylinder head side covers, which holes the points and point cam.

Once the upper case was cleaned, the crankshaft was installed with an endless camchain looped around the middle. The transmission gears were cleaned with a plant-based cleaner that worked amazingly well on the brown crud that was attached to all the rest of the internal shift and clutch parts. I have to say that this has been the most challenging engine repair I have attempted, given the amount of clinging oil deposits that attached to all the internal parts.

Amazingly, the transmission parts were all in decent shape after cleaning. Even the notorious low gear bushing still had the ridge in place. The gear dog engagement was marginal but acceptable. I replaced the shift drum with one with less wear and reused the shift forks. I had to hone the inside of one of the gears where the bronze bushing was binding on the shaft for some odd reason. Ultimately, the bottom end was reassembled, along with the clutch which had been fitted with a version of Barnett fiber clutch plates. The fiber plates were probably some of the Kevlar bits attached to the backing plates but with little round holes in the center of each contact patch. The thickness was around 3mm, but for a 5-plate clutch, the requirement is about 3.5mm. I had contacted Barnett about clutch plate kits during this time and they did show an unusual fiber plate pack that had both red and gray fiber material that was just bonded to the backing plates. I paid a bit over $100 for the set and had them set aside for the possibility of use in an engine project.

I used the older plate set in the clutch build, but added another metal plate to make the stack height more correct. 5X a .5mm thickness is a 2.5mm overall change in the clutch pack height. No matter which of about 5 different clutch packs that Honda used in Dreams, Scramblers and Super Hawks, the clutch pack stack height is always the same.

So, you can convert the early 6-plate clutches to a more desirable 5-plate setup, but the height must always be the same. A change in the stack height leads to issues with the clutch adjuster and clutch lifter parts in the kickstarter cover. When the height is altered, the index marks on the slotted clutch adjuster and also the angle of the clutch lifter arm don’t match the original setup and that can cause clutch release problems. Ideally, the clutch lifter arm should be pulling through an arc, below and through horizontal. When the pack is too tall, the lifter arm loses it’s leverage advantage and the clutch pull effort increases.

I have seen some over-tall clutch packs rub up against the inside of the clutch cover, as well. So, there is only one correct way to setup the clutch assemblies in these old bikes, no matter how many clutch plate packs it has. Ultimately, once the bike was up and running, the clutch slipped under high rpm loads and finding neutral was difficult. When the clutch was removed, the little rivet holes seemed to serve as suction cups, sticking the steel plates to the surfaces unnecessarily. I prepped up the new Barnett clutch discs and installed them. Because they were the correct thickness, the extra steel plate was removed and the stack height was just about right. The index marks on the kickstarter cover were close to factory alignment and the clutch didn’t slip under load and finding neutral was much easier. I always use the little steel retainer springs which are NLA in the world now. Depending upon the original clutch plate pack, the retainer wire grooves are machined in different locations to accomodate the thickness of the plate sets being used. The early 6-plate hubs have three grooves to set the Plate A, then two sets of steel and fiber plates. The later 5-plate hubs only have 2 grooves; one to set the thicker 3mm steel plate A and then one set of steel/fiber plates. You can’t mix and match these parts when changing the fiber plate count. It all has to match up correctly. Also the last version of the pressure plate has angled relief holes on the outer cover surface to help evacuate the trapped oil inside the clutch assembly. That last generation 5-plate clutch for CB and CLs are the way to go for good clutch performance.

Okay! Well, back to the bike’s challenges. The installed 3.00 x 18 front and 3.25 x 18 rear tires were placed with a set of 3.00 x 18 tires, which normally give sufficient clearance under the back tire when the bike is on the centerstand. As received the bike was sitting on all 4 points, so the rear was changed out first. In order to get some clearance on the rear wheel, I have to drag out a 1/2” steel plate that weighs about 15 lbs to slide under the centerstand feet, raising the bike up enough to R&R the rear wheel assembly. I changed the tire and reinstalled the wheel assembly, after cleaning rust out of the rear brake drum, and added a new rear brake cable. The tire was still kind of skimming the work stand, though. I put a jack under the starter motor which raised the front end enough to allow removal of the front wheel assembly. This was easier than usual, as the front fender was bobbed back about 6 inches.

Finding a correct 2.75 x 18 front tire is getting more difficult, so I just went with another 3.00 x 18 tire that matches the rear tread pattern. The new tire profile was shorter than the removed tire, so finally I got some ground clearance under the rear tire when the bike was sitting on the centerstand. Puzzling this out further, I noticed that the rounded feet on the centerstand legs were flattened out from wear, so that accounted for some of the clearance issues at the back. The bike still had the original rear shocks, set at the lower pre-load setting, so that wasn’t an issue.

After finishing off the now bright looking engine assembly, I tucked it back under the frame. It’s a delicate process and I do have a little sideways bike lift that I have used in the past to hold it steady while raising the 115 lb lump into the chassis. I also use a little Harbor Freight hydraulic jack that can be used with great care to avoid having the engine fall off sideways. I put the foot of the jack under the drain plug area to help give it some stability and slowly raise the engine upwards with a couple of long Phillips screw drivers to use to hold it steady as the holes align. Putting the breather hose on the cylinder head top cover and routing the points wiring lead up over the cylinder head first, saves a few steps later on. After re-attaching all the mounting bolts, the bike was finally coming back to correct appearance.

Watch for Part 2 coming up next....

Bill Silver aka MrHonda

www.vintagehonda.com

MrHonda’s Summer Tsunami..it’s a foursome.

I went from ZERO bikes in the shop for about a week or two, to four bikes all delivered in one day! As usual, it’s complicated.

My pal Gilles Brochard, who lives up in Carlsbad, had collected about 15+ vintage bikes over the past few years and after his divorce and uptake in his business work decided to divest himself of a handful of bikes.

This round included an unusual CA175 sloper, a 1969 S90, a 1965-ish CB160 and a 1975 CB400F. I expressed interest in the S90 and CB400F and we met for lunch and worked out a favorable price, but it included getting his 1966 CB77 back on its’ feet after a long sleep. The “other” bike in the mix was his CB350F which had also been resting in his garage unused. He had a buyer for that bike, but he was coming down from Pismo Beach to fetch it. Knowing that the bike had not been operated for awhile, the new buyer, Thomas, was wondering about who might be able to bring it back to life. Gilles said, “I know a guy.”

And so, I got roped into a drive up to Carlsbad to pick up the S90, while Gilles brought down his CB77 and the CB400F. Thomas had rented a trailer in Pismo and buckled down the CB350F and followed me down to Casa De Honda for a big Honda party. Thomas had bought a new battery and a set of my recommended #80 main jets for a carb clean and jetting update. I have re-jetted several of these bikes with bigger main jets and they all seem to enjoy the enriching experience, especially on our E10 gasoline that is in all California gas stations.

So, with all the bikes dropped off, Gilles took off for home, Thomas and his wife went to lunch while I extracted the carb rack and began to clean the idle jets, emulsion tubes, needle valves and install the new main jets. All told, the whole revival took about 5 hours, but the end result was just wonderful. The bike felt crisp and smooth with the new jetting. The timing was checked and the battery installed. The charging system was checked and he was good to go.

Meanwhile, the CB77 had fuel problems which required a petcock update, carb cleaning, and I installed a spare Pro-Trigger e-ignition system to help it get a better spark experience. The right side muffler o-ring seal to the header pipe was blown out, but fortunately, I had some spares. I replaced all the o-rings for the carb flangs and insulators and tucked it all back together again. It fired up quickly on its new battery, so that was one more completion done.

After the CB77 went home, my CL77 customer who lives in LA area brought back the bike with the rebuilt engine from a few months back to get it running again. They dropped it off and left, so I got to finish putting the rest of the bits back on. I was horrified to discover that for some reason the engine was barely able to turn over with the kickstarter. I panicked thinking that something had gone very wrong with the engine build. It’s a LONG story, but when they came back to pickup the bike, the kickstarter knuckle split and jammed the engine up tight. Apparently this was the cause for the original engine turnover issue, after all. There were some oil leaks to fix and I discovered that the bike had a 42t rear sprocket instead of a 37t standard gearing sprocket. After a number of hours of labor and more parts, it finally went home as a full-functioning 305 Scrambler. This was going on in the middle of all of the rest of these other projects.

The S90 was missing the rear turn signal bracket, but was otherwise in good shape. There was a tiny Motobatt battery that needed 2 days of charging to get from no volts up to about 5.6 volts. The carb needed cleaning and the little connector from the carb to the air filter was a piece of radiator hose. There was no baffle in the stock muffler and the carb main jet was increased from the stock #85 to a #95. I thought that might be a reasonable choice given the E10 fuel and the lack of a baffle in the muffler. After a thorough cleaning of the points, I finally got a good spark to the plug and it finally fired up on the fuel bottle. The tank has some rusty places inside, so will get cleaned and sealed. The petcock was rebuilt and some local driving hasn’t shown any signs of rust blocking the jets. I actually jumped the main jet to #100 because the new spark plug was coming out white on the tip. After some test runs, it finally started to show some color. It has ancient old stock sized tires on it and is pretty original with just about 4k miles showing on the speedometer. I finally had to spring for $125 for a new rear turn signal mount which is labeled for a CL90, but should still fit the S90 frame.

NEXT! The CB400F must have spent time near the beach and under a tarp, as much of the chrome had pits and rust on the surfaces. The worst part was that the tires were over-sized 4.00 rear and 3.50 front vs the standard 3.50 rear and 3.00 front. Peeling those 2008 date code monsters off the narrow rims turned into a huge wrestling match. Plus the front axle didn’t want to come out of the axle nut no matter how much force I used. I tried heat and penetrating oil and big metric wrenches. Finally I whacked the end of the extended nut a few times with a big hammer, which probably wasn’t good for the ball bearings and then used a chisel to catch the edge of the nut with a hammer and after about 10 blows it finally loosened up. I was concerned that I might injure my broken thumb again, but somehow survived the experience. I nice set of correct IRC tires were installed which improved the appearance, at least to me.

Eventually the forks came off for new seals. The right side came apart okay. You need to use a long 6mm Allen wrench to remove the bolt from the damper rod so the fork tubes can be removed from the sliders That side went according to plan, but the left side wasn’t having it. The hex head inside the damper bolt stripped out so there was no working with it until a new spare bolt as purchased from 4into1.com It will be drilled out and then the fork can be disassembled and the seal replaced. It’s not leaking too much at the moment, so that can be put on the back burner for awhile.

The bike’s Varnish Blue paint colors on the tank and side covers is in great shape, but the turn signals had been removed and the master cylinder replaced with an aftermarket type that wouldn’t mount a mirror on the right side. Fortunately, all the turn signal parts were included with the bike and the master cylinder might be suitable for a rebuild. The carbs came off and were suitably gummed up. They got a good cleaning and some #80 jets. An aftermarket muffler that looked much like the original but turned out to be WAY TOO LOUD once you throttled it up, so a OEM style replacement was ordered up from DavidSilverSpares.com.uk. They only had one left and unfortunately it wasn’t in the US warehouses, so the shipping bill was $80.

The bike fired up and ran well, except for the excessively loud exhaust muffler. The aftermarket muffler looked similar to the OEM version, but had a removeable baffle on the back end. I removed it to find that all of the fiberglass packing was gone. A new packing kit is on order. I took it out for about 15 minutes and was reminded about how these bikes felt to drive again. I purchased a new one back in 1975 and it wound up doing some Box Stock racing for a few races at Riverside and Ontario. Eventually, I sold it to my brother Jim, who drove it about 30k+ miles before trading it off for a 500 Interceptor. I’ve owned about a half dozen CB400Fs over the years. A lot of them got bought up and shipped back to Japan, where they are coveted. Ironically the JDM models are 399cc while the export models are 408cc, all because of the licensing restrictions in Japan for bike over 400cc.

My near-death experience was with a modded 459cc Yoshimura equipped bike that ran 115 mph, until my untimely collision with a bike that pulled in front of me while I was looking at my pit board. I rear-ended him and we both crashed at high speed. I photo of me flying in mid-air made the Cycle News feature story about the end of the 6 hour race. All the factory teams were there and after I was picked up and flown off the track in a helicopter, the results were that the Honda team with Freddie Spencer had one by 1 second over competing teams after 5 hours and 40 minutes of intense racing. That, needless to say was the end of my road racing career, having started with winning the 125 Production Championship in 1974 on a CB125S1. Ironically, once my multiple broken arm was healed up, I traded the race CB400F for a 1979 CBX six-cylinder!

After buying the S90 and CB400F, I noticed that the CA titles were a problem. The S90 had the same serial numbers in the frame and engine sections of the title, which is way wrong. The CB400F only has a frame number and NO engine number on the title. I will have to haul them back to DMV and get them inspected and new correct titles issued.

Next, after the CB77 was about to go back home, Gilles left a cute red CB160 for revival. It needed the usual new battery, carb clean, new tires and a fuel tank clean and seal. Plus, the speedometer bushing had seized up, so it was sent to my friends at Foreign Speedo for repairs. I soaked the gas tank with Costco vinegar for about 4 days, which worked great if you are not in a hurry. I used the Caswell tank sealer to complete the tank project.

Waiting in the wings is a rebuilt CB77 engine, for my recent new enthusiast friend, Mario. Mario got the vintage Honda bike bug and bought up about a dozen bikes without consulting the experts. He’s going to powder-coat the chassis and guess who gets to make a bike out of it? MrHonda. He also bought a complete CB77 and has just asked if I can bring that one back to life again.

There is another N. County CL77 that needs to be revived soon, plus TWO MORE 250-305 Scramblers coming in a month or so from LA. One only has 975 miles on it! As Sonny and Cher sang, “The beat goes ON”

Bill Silver aka MrHonda

www.vintagehonda.com

Stepping out on a branch…. SL350 twin.

 The wave of various “opportunities” keep coming this year. Recently, a call from my new friend Doug, who was referred to me by my other buddy Bill, made a different than usual request. This time, Doug wanted me to disassemble a SL350 engine completely, so he could vapor blast all the external surfaces, then bring all the bits back to me for re-assembly.

                                                 SL350K1 image courtesy of AHMC.

I had a little lull in the action in the garage, so offered to take on the challenge. Doug brought the engine down on a Friday morning and we twisted, hammered, and dismantled the big lump in about 2.5 hours. Doug had already removed the clutch cover, top cylinder head cover and clutch internals, plus the dyno cover side stuff.

This was basically a “virgin” engine which had not been dismantled previously, so the screws, bolts and nuts were all sitting cozy together in the past 55 years. I laid out some demolition tools and we began the work. Doug is a big, strong man, despite having his own set of motorcycle related past injuries to his wrist and back. Having him hold the engine core steady while I was pulling, pushing, pounding and twisting the bits was very helpful!

The first task was to remove the two cam sprocket mounting bolts. NOTICE! The two bolts are NOT the same. One has full threads and the other one has an unthreaded shoulder. IF you accidentally swap the bolts to install, the end of the camshaft mounts break off and the cam is ruined.

Starting with the two cam holders, held together with 4 Phillips screws, I started by inserting the impact driver #2 bits into each screw head and pounded the bit a few times with a brass hammer. I followed this by inserting the tool bit back into the driver body and started whacking at each screw. The first round was 2 for 4 successes. I upgraded the hammer to a 3 lb sledge hammer, but with no further progress. Plan B for this situation is to use a long chisel to catch the corner of the screw head on an angle and start hammering again. After another 30 seconds per screw, all four were released and removed on the tach drive side.

Turning the engine to the point plate side, the plate screws were removed, more easily because they had been loosened before for ignition timing adjustments. Once the point plate was out of the way, those 4 screws were clear to attack. This side mirrored the first side…. 2 for 4. Another round of chiseling the heads loose gave way to parts removal, at last.

The camchain tensioner was unbolted from the back of the cylinders to release the camchain tension. This allows the camsprocket to drop down on the shoulder of the camshaft allowing the cam to be wriggled out carefully through the right side of the cylinder head. The camchain is endless and the space allowed on both sides of the sprocket with the chain installed is insufficient to just drop the chain down off the sprocket. Conversely, the chain and sprocket will have to be mated together before the cylinder head and is installed.

Once the camshaft is removed, the cylinder head will come off once the two small 6mm bolts are removed next to the spark plug holes. A step that I missed earlier was to loosen the rotor bolt to allow the rotor to be removed with the correct 16 x 1.5mm removal tool. Using the engine’s compression and the internal friction of the pistons and cams, helps keep the rotor from turning easily while removing the bolt. My battery powered impact tool decided to take a nap, so we finally had to put a long screwdriver through the rod ends, after the pistons were removed and a foot long 1/2” drive breaker bar with 14mm, 6 point impact socket finally released the rotor bolt. An air impact would have done the job more easily, but was not available.

Once the head was removed and checked for valve condition and carbon buildup, it was set aside while the cylinders were lifted up to examine the bores and the pistons, plus checking the end gap of the rings. The engine was remarkably clean inside, with little wear shown on the piston skirts. While the cylinder bores didn’t show any ridges or scoring, wiping them down revealed some rust rings on both cylinders in almost the same location for both sides. The marks were about 2” down from the top, indicating that the bike sat for a prolonged period of time with the pistons sitting perfectly still at an almost even place.

The ring gap came out about. .020’ using the top ring inserted just below the top of the bore. This is pretty wide considering the new readings would have been about .006-.013”. The oil ring would have had only .004” to start life with. Clearly, we are at a crossroads about the next steps with the cylinders and pistons. The cylinders will require a good wet-hone treatment to clean up the bores, set up cross-hatching for the rings to seat in and hopefully minimize the rust ring damage. Interestingly enough, the bike had been running well and the spark plugs came out with a nice clean burn appearance.

With pistons removed, it was time to split the cases, after removing the oil pump and clutch basket, then pushing out the shift shaft, which snagged a bit inside the cases. Apparently the drive chain had been run loose and put some little notches in the shaft causing removal difficulties. Once the shift shaft was removed, the shift drum return hardware was lifted away. The kickstarter shaft is held inside the cases, so that had to wait until the cases were completely split.

More screws, 6mm bolts and 8mm nuts were wrenched loose, usually with a snap/crack sound as they gave up their years’ long grip on the engine cases. A few whacks with a plastic dead-blow hammer broke the case sealer bond and allowed the cases to be separated. The transmission counter shaft seal seemed to have been glued to the engine cases, so one shaft was stuck in the top case and the other one in the bottom case. Eventually it all came apart and the stout transmission components were set aside.

The shift forks are retained in the shift drum with little steel pins, held in place by small springs. Fishing the pins out required a strong magnet and screwdriver tip. The shift drum was slid out of the upper case and the crankshaft holders were left to remove once the long bolts were broken loose and set aside.

BIG NOTICE! In the bottom case, there is a small but critical plastic round ball which is inserted before the engine cases are reassembled. The ball is situated just about the oil pump outlet passages. IF the ball is not replaced, the engine will never see oil to the top end and the camshaft will seize in the cam bearings.

Image from Honda 250-350 Shop Manual

Doug hauled the boxes of parts away for cleaning, while I gathered up parts for the rebuild. Sidebar story to include was as Doug drained the oil and began to remove the dyno cover, a small steel curved piece of metal appeared. The engine was described as being a bit noisy with a growling noise coming from the bottom end. The metal piece was actually a 1/2” of the main bearing ball retainer. I’ve never seen this kind of bearing failure before and it could only be some kind of manufacturing failure from the looks of it. Finding a new bearing was a challenge as the two listed on eBay were $80 and $100 plus shipping. A full web search didn’t come up with any other findings. The bearing is not modified with a locating groove or pin hole, so I am surprised that a standard replacement bearing can’t be found.

What we discovered is that the listed 6206 bearing on current Honda microfiche listings is INCORRECT. Who knows why Honda chose an obscure one-off crankshaft bearing. From checking the CB350K0, I see that they started out using a roller bearing and cage, somewhat like those used on the 250-305s. Apparently that design wasn’t up to the task and they chose an obscure sized bearing to take up the spaces. The listed 6206, as we discovered was about a 1mm too small in the OD, so rattled around in the engine cases. Honda superseded the original roller bearing with a 91001-312-014 part number which is now NLA, world-wide. Doug did some digging and found the correct bearings in ITALY for $26 each, plus $50 shipping. He bought the two shown as available and now we sit in waiting for the correct part to reassemble his engine. With so many engines having been produced, the supply of crankshaft bearings over the past 56+ years has gone to zero.

Honda, reportedly produced about 600,000 250-350 engines. Parts lists show the early roller setup into about 1971. The rotors on the 350s are a solid one-piece design vs the layered and open type used on the 205-305s, which are the same diameter. Perhaps they were either heavier or had stronger magnetism which put more strain on the crankshaft bearing. Rather than redesign the crankcase bearing bores to fit something conventional, they seem to have chosen to have the bearing company design a specific bearing just for the 350s. Being that my focus is on the 250-305 engines, we both learned some new and unsettling discoveries about the 250-350 engines. My riding experience with 350s is that they vibrate heavily, causing fasteners to loosen up and the mufflers to suffer failures internally, if they haven’t rotted out by now due to condensation damage. Perhaps the additional engine vibration generated forces that damaged the original bearing designs.

A few weeks later….

Doug had all the parts sparking clean and ready for reassembly, as we began to assemble the bottom end, we discovered that the “CB/CL/SL350” seal kit from my usually reliable 4into1.com came up short with the big, thick, triple row transmission shaft seal. Going back to the site, the seal was listed separately, but with no real notes about the fact that it needed to be included with the rest of the seal kit.

This brought the reassembly to a halt, while we decided what to do next.

"Next" was to put the cases loosely together and assemble the top end. You have to put a little wire on the endless camchain, as it gets drawn upwards through the engine top case, the cylinders and eventually to the cylinder head. The part that has made me uneasy in the past was the goofy lower end of the camchain tensioner with two rollers. The bottom end of the tensioner arm is held, somewhat loosely with a hollow pin with the ends half cut away and two tiny little rubber keepers that fit into the ends of the pin and then the whole thing sits down inside a groove in the top case. There is nothing to keep the parts from moving around or exiting their locations until the cylinder base gasket is installed. And even then, there is not a lot to keep things secure there.

We fitted the pistons back onto the rods, after the rings were installed. The replacement ring set had a 3 piece oil ring design. The top compression ring is shiny on the edges and the second ring black and seems to be flat on both sides instead of having an undercut around the bottom edges for scraping oil off the cylinders. We fitted the cylinders down on top of the pistons and the rings went into the bottom cylinder bevels fairly easily. Unfortunately, we overlooked that he camchain tensioner roller assembly hadn’t made it inside the cylinder cavity. So, back off the pistons to position the tensioner inside the central cylinder block cavity. The rings seemed to have decided to hang somewhat on the right side, even though they appeared to be well inside the cylinder bores. We double checked the three piece ring set as the central expander ends must just butt up against each other and not overlap. We dismantled the ring set to verify that the expander and rails were all properly installed in the ring lands and finally it gave up and let the cylinders fall fully down on the upper crankcase. All of this movement back and forth of the tensioner had me concerned about whether the little end bits were staying in place. I actually put a dab of sealer on the ends to see if they would stay put, but once the cylinders are down on the base gasket, there is no way to determine if everything is still in place. It’s a horrible design in my opinion.

The next challenge was to loop the camchain over the camsprocket and then feed them both up through the narrow opening in the cylinder head. We wrestled with the camchain and sprocket as the camshaft was inserted, but Doug finally noticed that the head was not all the way down on the head gasket and dowel pins. I put a small socket on the end of the cylinder studs with a nut to hold it all in place while we wrestled with the camchain and sprocket. The chain kept skipping off of the crankshaft sprocket causing the camshaft timing to be incorrect. I withdrew the camshaft, pulled up on the chain until it felt like it was engaging with the crankshaft sprocket and positioned the cam sprocket once more while we slipped the end cam bearing on one side to hold the camshaft in place. We fed the rocker arms and adjuster shafts into the cam carrier and then fiddled with the rocker arm position by moving the crankshaft back and forth just enough to get the rocker arms off the cam lobes enough to take tension off of the camshaft and finally install the cam bearings with the gaskets in place.

It’s a very tedious task overall. I haven’t wrenched on a 350 for several years and ever time it was a struggle to get it all right. I’ll gladly stay in my lane with the known 250-305s, thank you.

Doug ordered the special seal and had it delivered to his home, so he could complete the assembly of the lower end and finally button it all up for the last time. I’m available to consult on the final touches of setting the points and ignition timing, plus helping advise the setup of the carburetors as it finally goes back together for the last time. As Doug left with the remaining parts in hand, I reminded him not to forget the little plastic ball in the engine cases!

Whew! I’m going to pass on any further 350 twin engine work in the future. I’m still puzzling over the odd crankshaft bearing issue that is bound to arise for other 350 engine builders. It seemed like Doug found the last two bearings on the planet. What happens to the next guy who needs a crankshaft bearing?

Bill Silver

www.vintagehonda.com

www.mrhonda.guru

We Three Dreams… disoriented are…

So, currently a “1969” registered CA77, which was dormant for awhile was delivered from OC this week. It arrived with the top half of the carb attached to the air filter tube and cable, but was missing the float, needle and bowl.

        The bike has a 23,000 series serial number, which should be a 1966-67 model. Many Dreams sat in dealerships for several years after production ceased in 1967. They were often titled in the year of sale, causing confusion for buyers and owners who are looking for parts. The white tag on the harness relates to the year of manufacture for the HARNESS, not necessarily the year of bike production.

I ordered a big batch of cables from www.classichondarestoration.com, and started in on the remains of the carburetor while I waited for parts. I discovered that the slide needle had NO numbers stamped on the place just below the clip notches. That usually means that the needle came from a Keyster kit, which usually have a DXX number stamped on the part. I scanned eBay sellers and just one had new OEM needles for sale for $20, plus shipping. In this case, the number was 22401.

A while back I also was given an early round bowl CA77 carburetor, but it was missing the top, slide and needle. While I had the ultrasonic cleaner working, I decided to clean both carbs at the same time. The last known part number ends in 030, which means that there were three versions made for the 305 Dreams. Apparently there was no 266-000 version. I was well aware of the round vs square bowl options, but had never really closely inspected the other differences.

                                                        Late square bowl CA77 22mm carburetor

  I discovered that the main jet holders were threaded differently.

 Looking at the pilot screws, one had a notch for the o-ring and the other one didn’t. Looking at the carb bodies where the pilot screws are installed, one was clearly machined for an o-ring and the other one was threaded all the way to the top.

                                                                            

                                                  Different machining on the air mixture screw ports.

I discovered that this late carb had a flapper door choke plate vs the early solid plate type.

                                                    Late vs. Early choke plates.

The floats are obviously different but the early rounded floats can be replaced with square bowl floats with no problems. The latest floats are actually labeled 286 for the CB250 version of the CB350 twins.

The flame arrester screen on the early bodies were pushed on over the intake opening, whereas the later ones were nestled inside a machined surface of the carb throat.

As I concluded the cleaning of all the parts, making sure that the jets were open and the various air bleed ports and bowl vent passages were open, I tried to install a spare float bowl from one of the 250-305 CB/CL square-bowl carbs I have lying around. When the bowl was fitted to the body, it stopped short of meeting the gasket surfaces. You could hear and feel that something was hitting up inside the bowl. Looking closely, it was apparent that the float bowl overflow tube was striking a portion of the bowl roof! All the float bowls I have handy were all the same except for ONE. This bowl had an overflow tube that was just flush with the gasket surface of the bowl, instead of the others which are an 1/8” proud of the gasket surface area. That bowl fit right onto the carb body allowing the clip to secure it to the gasket. The odd thing was that the bowl didn’t have a drain screw at the bottom.

The first generation round-bowl Dream carbs had a straight out screwed-in fuel line fitting. It had to be removed before the carb could be installed or removed, as it hits the frame, preventing removal or installation. This late mode. carb came with a banjo fitting like those used on the CB/CL carbs. The last square bowl carbs have been seen with a short pushed-in fuel line fitting. The jets are all the same JIS thread pitch types, but one wonders if the later replacement carbs, issues after the end of production and during the transfer from JIS to ISO thread pitches might have some surprises awaiting the owners.

So, that’s the scoop on Dream carbs, as far as I can tell. Apart from jetting components, the CA72 carb body would probably suffice as well. Both are 22mm mixers. Honda did offer some C/CA72 Dreams with an unusual Mikuni carburetor option. The suffix for those parts ends in -005 vs. 004 for Keihin types.

Bill Silver aka MrHonda

www.vintagehonda.com

05/2026

A 1967 CL77 service visit develops into a major event….

 My customer Paul has a bike that belonged to another customer a few years back. He contacted me about finding a suitable CL77 for sale and I hooked them up which resulted in a transfer of ownership.The bike is a 1967 model, originally one of the Candy colors, but Paul wanted the Silver/Black look, so he had the tank and side covers painted. The bike had been in previously for some running issues, thought to have been solved, but arose once again. Plus the nuts that hold the rear sprocket on were never tightened properly and three spun off. He was able to recognize the problem before it put him on his head. He complained that it sometimes idled too high and sometimes died at idle. There was restricted power in intermediate gears and it just wasn’t a very happy machine. He actually rides the bike around San Diego regularly, so reliability is important, of course. One issue was the sudden high idle when the engine speed was above 4000 rpm and stayed high even with the throttle closed.

The bike arrived on the back of a roll-back tow truck. In the unloading process it almost went down before we caught it just in time. I had lined up some nuts and studs for the rear wheel, so that was the focus at first. Then I went through a compression check, which came up with 165 psi on the right side and 90 psi on the left. Checking valve clearances didn’t seem to be related to the problem. I pulled the slides out and raised the needles a notch, checked the ignition timing which was a Pro Trigger electronic conversion and everything looked pretty standard. There wasn’t a lot of gasoline in the tank and the bike has no crossover tube, which was an odd feature of the 1967 models. A quick test ride didn’t feel quite right and a longer one developed a dropped cylinder on the way back. Checking fuel in the bowls, the right side was fine, but the left side was empty.

This gets into a not uncommon fuel flow puzzle where a twin carb engine has fueling problems to one side, even though the petcock is clean and both outlets are open and flowing. Somehow an air lock happens or the uneven length of the fuel lines causes a fuel disruption to one carburetor. As a test, I removed the fuel lines at the banjo fittings and cut about an inch and a half off the longer hose. Taking the same long test ride with an uphill climb resulted in normal performance once again. So far, so good.

I encouraged Paul to hang around and watch what all I was doing and the challenges of working on the CL77s, especially. The next request was an oil change and filter clean. On the later engines with the “big hole” clutch covers, you can fish out the filter and chain for service without needing to pull the whole clutch cover as was required in the earlier models. Well, the oil, which was last changed 800 miles previously, came out with fine metallic particles visible in the oil pan. The filter had a thin layer of debris, but some disturbing signs of tiny pieces of brass embedded in the filter debris field.

I noticed that the engine was louder than normal, somewhat sounding like it had loose cam chain tension, but it was difficult to pin down exactly while running. I hypothesized that perhaps the low gear bushing was wearing out causing brass filings to be deposited into the oil. Obviously something was wearing inside the engine and Paul authorized me to dig into it. This, of course, requires about an hour of dismantling the engine from the chassis and getting it up on the work bench. Paul watched as I heaved all the brackets, bolts, screws and pieces into a plastic bin for the removal process. He helped me haul the 100 lb lump out of the frame and onto a dolly where it was pushed over to my messy work bench. I had just dismantled a CB77 engine (separate story) so there were bits of it here and there. After some 4 hours of wrestling with the bike’s problems and now engine pull, we called it a day and waited for the big reveal on Saturday morning….

                                                    Loose/worn camchain does this to the cylinders.

The engine was waiting for me to do some magic and I dug into it with hopes of finding some remedies for what seemed to be unusual wear issues inside. The clutch cover came off and all of the primary chain bits removed to facilitate splitting the cases. I noticed that some of the bottom fasteners and the sealing washer were previously removed, so it was difficult to say what would be found. Once the cases were split, the transmission gear dogs showed excessively deep engagement, which turned out to be that offset gear cotters were installed on the transmission gears. In earlier years, the transmission parts had straight cut gear dogs which didn’t have sufficient engagement. This caused the transmission to jump out of 2^nd gear. Honda issued a TSB for this problem and the release of these offset gear cotters which moved the gears closer together ensuring clean gear shift selection. In the later transmissions, the gear dogs were back-cut to promote engagement and secure gear selections. Some gears were updated to reduce the amount of side-play which aggravated the gear dog engagement issues. This alleviated the need for the offset cotters, for the most part. When the cotters, which come in two offset sizes, are used excessively the gear dogs can rub against each other in neutral, generating a clicking noise.

When the bottom case half was inspected, most of the metal debris was right below the transmission gears indicating that some unwanted contact was being made. I removed the offset cotters and installed plain flat ones and the gear dog overlaps were still well within recommendations. I noticed some main shaft side play where it pushes against the edges of the brass bushing in the transmission’s top gear output shaft. I had a new transmission gear in stock but the sprocket splines were deeper than the 1967 shallow spine pattern. That still works as the shallow spline sprockets fit the deep spline versions. The new gear reduced the shaft side play. The end of the bushing is proud of the surface of the shaft so gets contact from the steel end of the main shaft, causing some eventual wear.

The low gear bushing was replaced and fortunately the kickstarter pawl wear was minimal, so it was time to put the cases back together once again. I rolled the engine back upright and noticed a lot of baked-on yellow substance around the head gasket area, as if someone had been trying to seal up an oil leak. I called Paul to let him know that the head gasket was probably leaking and someone had previously tried to seal it up from the outside with an unknown substance. Paul agreed that the head should come off, which also gave me an opportunity to check the wear on the pistons, rings and cylinder walls, along with any valve sealing issues.

                                                

                                        3M glue?  Unfortunate attempt to seal a leaking head gasket

Talk about opening a can of worms….. The top cover and breather plate came off easily and the cams looked fine. Once the cylinder head was pulled there was some discoloration on the cylinder walls along with a bit of scuffing on one side. The cylinders were still on STD bore sizes from the factory. When the top piston ring was removed from one piston and inserted into the cylinder bore, the end gap of the ring was about .024” which is at the far end of the service specs. New rings in fresh bores are normally about .008”. I tried a new CA77 top ring in the bore and the gap was .015” so a good hone job on the cylinders and fresh rings should have it running well, saving $300 for new pistons, rings and a bore job. New STD piston rings were sourced from my friend Ed Moore, who is winding down his engine rebuilding business. I had the cylinders honed at a shop about 18 miles away.

The valves were coked over with old burned oil and gas deposits. Removing the valves requires taking the side cylinder covers off, loosening the tappet screws and then pulling the rocker pins out. As usual, what I see on running engines is that the intake valve seats are wide and shiny, with the faces of the intake valves somewhat cupped. The exhaust seats are somewhat wide and often have little dimples in the valve seats where carbon has been trapped at times. The valve seats are part of the cast-iron skull which is cast into the cylinder head. In the days of pre-unleaded fuels, the lead in the gasoline provided somewhat of a coating to prevent wear on the seats and valve faces. When unleaded gas came available, vintage cars and motorcycles often experienced sinking of the valves into the seats, requiring a machine shop procedure to install hardened valve seats in the cylinder heads. This isn’t an option for 250-305 engines and for the most part, it isn’t a problem as these engines are not used in regular transportation these days. Generally, the heads are taken to the machine shop for new valve seat cutting and then new valves are ordered to make it like new again. Honda’s exhaust valves are about $100 a pair and the intake valves somewhat cheaper from www.davidsilverspares.com I do have some factory valve seat cutters that can clean up the seats if they are not too badly worn. But that’s not all!

Looking closely at the cylinder block, I noticed a groove that was worn in the inside of the cam chain tunnel where the cam chain has been rubbing against the alloy block. This was quite possibly the source of the non-metallic debris floating around inside the oil supply. So, now we have to find a new cam chain. Also, the center guide roller was all chewed up, requiring replacement. I keep a few of these in stock for such cases, as Honda no longer produces them. You can see that the bill for labor and parts is continuing to rise exponentially just to rebuild the engine, not to mention the extra hour it takes to reinstall the engine and hook everything up once again.

This job came back to bite me when the engine rebuild was done and installed, the hanging high idle condition remained. I did notice that turning the point cam to check the advance/retard function had a little bit of a click step in it. What I didn’t notice was the point cam plate, deep inside the camsprocket was cracked in half, from some previous repair attempt. I failed to check the condition of the plate inside the camsprocket.. This split plate engaged with the point cam tang okay at idle, but as the revs increased, something got cocked inside and caused the weights to hang open until the engine rpms were reduced either on a long slow deceleration or in gear when the brakes were applied which slowed the engine speed down to where the weight springs took over and returned the point cam back to the idle setting.

I spent another 2 hours extracting the camsprocket, while the engine was still in the chassis. You can only do this with a Scrambler, because there is sufficient clearance above the engine that allows the top cylinder head cover to be removed. The locking nut on the camshaft sprocket was nudged loose with a long flat blade screwdriver that had a plastic handle. It was tightened in the same manner. Both camshafts have to be driven out of the head, but the process of removal keeps the inner camshaft bearings in place. Once the new camsprocket is placed into the head, the master splines on the cams and camsprocket have to be all aligned for installation. It’s probably not a task for beginners, but it did turn out well in this case, as I have done this procedure once before.

With everything all buttoned up, the test ride was unremarkable in that all functions were working normally this time. All it takes is to miss inspecting a critical part like this and everything goes sideways.

Such is the life and trials of MrHonda in 2026!

Bill Silver aka MrHonda

www.vintagehonda.com

04/26