Pointing to the past…

I subscribe to many FB forums, plus have my own stream of customers who contact me through my website: www.vintagehonda.com for help with their 50-60+ year old vintage Hondas. For those who are coming new to the hobby and the mysteries of old-school motorcycles, the subject of “points and condenser” ignition systems comes up often. In the 21^st Century, the prevalence of electronic and CDI ignition systems overshadows the 20^th Century ignition systems, which appear primitive by design.

The points and condenser ignition system, originated by Charles Kettering, is described on many websites like: https://ratwell.com/mirror/users.mrbean.net.au/~rover/ketterin.htm and

https://www.wikiwand.com/en/Ignition_system

As applied to vintage Honda motorcycles, the function is the same as the automotive systems, which had distributors to feed sparks to multiple cylinders, one at a time. On a simple motorcycle engine, the ignition systems started out with self-powered magnetos, which mostly have a fixed ignition timing and do not require a battery to power the units. 

Early Honda 50-70cc models all have magneto ignitions, most of which are fixed spark advance designs. Small-bore engines can run successfully on a fixed ignition as they are easy to kick over and start and the spark timing doesn’t cause undue engine heat buildup as what would happen on a larger displacement engine. In the case of the first-generation Honda Cub 50cc models, the kickstart models had 35 degrees of spark timing built-in. However, the electric-start C102 models needed a retarded spark timing to allow the starter motor to more easily turn the engine over at cranking speeds. So, only those models have a mechanical spark advance system built into the flywheel.

Magneto ignitions use a set of contact points and a condenser to manage spark production. They are “live” all the time, so in order to shut the engine off, you have to have a “kill switch” of some design to short the primary voltage to ground. When Honda went into the realm of CDI (capacitive ignition systems) in the late 1970s, they were also self-powered and required a kill system to shut down the sparks.

In their basic form, the ignition points are a variable switch that turns the ignition coil on and off. They are variable, in that the point gap can be adjusted by changing the point base in relation to the spring-loaded, movable point arm, which is operated by the rubbing block. The rubbing block rides on the eccentric point cam and follows the profile of the cam lobe.

                                                  Drawing from AHMC training materials

The problems with the point system are that the rubbing block eventually wears down a little at a time, which reduces the point gap. As the gap decreases, the opening point becomes later and later, which delays the spark timing to the engine. On a normal tune-up, the contact faces are cleaned with an abrasive to increase metal-to-metal contact which ensures more voltage going to the coils. Then the point gap is enlarged by the adjustment of the point base screws. This brings the ignition timing back to factory specifications and ensures proper engine performance. To reduce the amount of wear on the rubbing block, high-temperature grease is used to lubricate the point cam. On some point plates, a piece of oil-absorbing felt is located next to the point cam and a drop of engine oil keeps it wet and lubricated.

The point contact faces are generally made from a metal called tungsten, which has high resistance to arcing and metal transfer when the points open. When the points are closed, the current is allowed to flow through the ignition coil building up a high voltage charge. When the points are pushed open by the point cam, the voltage flow is interrupted and the points are subject to an arc/spark which jumps across the faces as the voltage tries to maintain the connection. The use of a condenser in the circuit absorbs the arcing force momentarily, then discharges it back to the ground when the points are closed again.

In battery-powered ignition systems, the power flow is from the battery to the ignition switch, then to the ignition coil. Some models will route the power through a handlebar-mounted kill switch so that the ignition can be switched off quickly in an emergency or to shut the bike down without reaching for the ignition switch. A defective kill switch can cause “no-spark” issues when the contacts become corroded or the connecting wires to and from the switch are loose or grounded by a pinched wire in the handlebar switches.

When all the wiring is intact, the battery voltage routes to the ignition coil which generates several thousand volts when the points are closed. The coil discharges the spark energy when the points are opened, dumping the high voltage out of the spark plug wire to the spark plug where it jumps the plug gap and creates a kernel of energy that ignites the fuel/air mixture inside the cylinder’s combustion chamber.

The timing of the ignition is critical to the engine’s performance as the fuel mixture is compressed prior to combustion. At slow idle speeds, the spark timing should be about five to ten degrees before top dead center on the compression stroke. As engine speed increases, the time available for the combustion charge to ignite also needs to speed up, and the spark timing is advanced by the point advancer unit.

The spark advancer is generally a system of weights and springs where the springs hold the weights in retarded mode and then the weights will overcome spring tension as the centrifugal force increases with engine RPMs. The weights pivot on locating pins and interact with the point cam at the base where the point cam rotates on the advancer base shaft. The point cam then shifts the opening moment earlier in conjunction with the increase in engine revolutions. Full spark timing advance generally occurs about 30-45 degrees before top dead center of the piston above 3,000 RPMs.

The configuration of the engine in regards to compression ratio, cam timing, and shape of the combustion chamber dictates how much spark timing is required to make the best use of the fuel available. When spark timing occurs too early or late, fuel energy is wasted and results in unburned fuels going out of the exhaust system which is a major contributor to air pollution as well as poor engine performance and dismal fuel economy results.

Spark timing directly affects the engine’s manifold vacuum signals to the carburetor metering circuits. As spark timing advances, the engine vacuum signals rise pulling in more and more fuel through the idle and main metering channels. In the case of the archaic spark advance systems in the 1960s Honda 250-305cc twins, the mechanism for advancing the spark timing is inside the camshaft sprocket and not serviceable without engine removal and splitting the two cams apart in order to remove the sprocket assembly.

This system, designed in the late 1950s, seems to be compact and self-lubricating, however, problems occur when the springs lose tension, the weights wear out on the pivot pins, and the little molded rubber stopper cushions on the weights either compress or dislodge from the weight faces. Furthermore, the camsprocket is basically riveted together and the rivets loosen up after many miles causing erratic camshaft timing as well as ignition timing irregularities.

All of these factors create a condition where the spark timing advances prematurely at idle from the normal five degrees before top dead center to twenty or more degrees. With increased spark timing the engine responds by speeding up unnecessarily. The engine speed increase causes more fuel to be drawn through the idle circuits further fueling the tendency to increase engine speed further. This snowball effect overcomes the carburetor’s ability to control idle speeds by the use of the idle speed screws and idle mixture screws.

On the market now are several electronic ignition systems that do away with the points and condenser, but still rely on the mechanical spark advancer for that function. These systems are magnetically triggered and are mostly immune to any wobble at the advancer in the case of the 250-305s.

https://www.vintagehondashop.com/ offers the most affordable solution to replace the twin sets of points and condensers of the CB/CL72-77 Honda twins (1961-67) for $159, as well as a designated system for the single point 250-305 Dreams ($139) plus a regulator-rectifier for $39.

There are other companies offering ignition systems for vintage Hondas including Charlie’s Place https://www.charlies-place.com/ and a company in Germany that makes a crankshaft-mounted system for the 250-305 twins. https://www.elektronik-sachse.de/shopsystem-3/en/digital-ignition-zdg-3-23-for-honda-cb72-77.html Prices range from $250-400+

While OEM points and condenser ignitions were perfectly fine for their uses when the bikes were built in the 1960-70s, the new electronic systems are maintenance-free and provide a clean trigger signal to the ignition coils for a fast and maximum spark burst to the spark plugs. Maybe it is time for you to bring your bike’s ignition system up to 21^st Century specifications now.

Bill Silver

aka MrHonda

www.vintagehonda.com

What’s next? A pair of twins…

Having just cleared off the work table lift of the last CB77 project, I was contacted by my friend Michael in Orange County who had rounded up a pair of CB175s. Both bikes had very low miles showing on the odometers, but the mileage indications were backed up by the fact that three of the four tires on the bikes were original Yokohama tires. Someone had replaced the rear tire on one bike with a 3.50×18 tire, but the edges were getting chewed up from contacting something inside the fender area, so it needed to be replaced as well.

The pretty turquoise bike was from late 1970 production with a 5 (K5) serial number. The bike had the original front brake light switch embedded into the cable, but the handlebar bracket was black on the bottom and shiny silver on top. Apparently, someone tipped the bike over, broke the bracket with the mirror hitting the ground, and then replaced the lower half of the switch with one from a 1972-3 model. The other concern was that the clutch lever was VERY HARD to pull in, indicating the possibility that the clutch springs had been replaced unless the clutch was stuck or the release mechanism is rusted up.

The bike has been refitted with an electronic ignition, but the engine was not running well on one side. Compression readings were 175psi and about 155 psi. The spark plug came out looking kind of oily wet, so it is possible that the engine was overheated and had a partial seizure, causing oiling of the plug.

The Gold bike had not been run for a number of years, so would need the most repair work, but you never know until you dive in and find the problems and solutions.

On to work…Goldilocks goes first

I rolled the gold 1971K6 bike up on the work bench, drained the dirty oil and checked all of the valve clearances first. The carbs were gummy, so were removed and cleaned in my little ultrasonic cleaner. It is always necessary to replace the flattened out o-rings on both ends of the manifolds, which I happened to have in stock. Speedometer was reading about 2800 miles and the front tire was the original Yokohama while the back one had been replaced with an over-sized 3.50×18” CS brand tire.

The left air cleaner cover had a broken tab on the rear which had been glued up with some unknown adhesive but broke again. I wound up replacing all of the frame rubbers for both side covers and used JB-Weld to repair the broken one again. Silicone grease was used liberally to rubber and side cover tabs to reduce further damage.

The Charlie’s Place e-ignition system had been installed with a new coil, but giving the trigger wheel a twist with my fingers revealed that the spark advance function was locked up. The spark timing setup didn’t look accurately installed either, as the magnets were not aligned with the pickup module center-line. The spark advancer assembly was pried off of the end of the camshaft and using Charlie’s online PDF installation instructions the advancer was disassembled and a small locating pin was ground down to allow the ignition rotor to fully advance normally. Setting up the timing is easy with these systems as you only need a 12v test light to probe the connector wires and turn the engine until the F mark lines up. If set correctly, the light turns ON and you are good to go.

After refilling the engine and reattaching the carburetors, I fed the carbs with a remote gasoline tank and fired the bike up. It sounded pretty good, but started to run rich at idle even with the mixture screws out way beyond normal. All the carb jets were OEM parts, but either the idle jets had been enlarged or perhaps the floats were sinking. Compression readings were right about 160-165, so the engine seemed to be sound and should be with 2800 miles showing on the odometer. The valves were adjusted, but were pretty close to specifications.

The gas tank got a phosphoric acid treatment followed by a dose of Caswell epoxy tank sealer product. The petcock feed tube was missing, so the remaining part of the tubing was drilled out and a 4mm tube installed in order to save the part. New gaskets and a screen brought it back to normal function again.

I got an unexpected box of spare parts in the mail from Mike, including an invoice for about $800 for work to install the e-ignition system from a previous repair shop. There was a few lines that included a camshaft and spark advancer too. In the box were the broken parts, including a camshaft with the spark advancer portion broken off and the advancer with the end of the camshaft still stuck inside. Obviously, the ignition system installation went sideways and a lot of money and parts were needed to make it whole again. The date on the invoice was 2019! You just never know about these things...

The next day…

After cleaning the carbs carefully, earlier on, the only remaining reasons for rich idle mixtures are idle jets that are too large, sinking floats or blocked air bleed passages. First pass was to remove the OEM idle jets and compare them to some spare a/m jets that were leftovers from a different project. I use a set of tapered jet reamers to clean out jets or just as a gauge to see if all the jets are the same size. The removed jets swallowed the whole jet reamer that was barely able to fit through the replacement jets. Using one of those cheap welding tip cleaner tools, it appeared that the jets were bored out to somewhere in the #45-48 size! Mystery solved, as the replacement jets cured the idle problem completely.

All that remained was to change both tires/tubes and take it out for a good test drive to check out everything else before turning to the little turquoise bike. The tire change took an extended period of time, as the brake drums and inside edges of the rims were rusted and needed a fair amount of time with a rotary wire brush and scraping with a flat-bladed screwdriver. When bikes sit for a long time, the air pressure drops down to near zero and the tires come off of the beads allowing moisture to enter and create rust spots. It is pretty much expected on bikes that are 50 years-old now.

If the same guy worked on both bikes previously, I had a road map of what to expect on bike #2.

Little Blue Boy, bike #2

This pretty turquoise 1970 CB175 had the stock muffler on the left side and a 354 code CB200T muffler on the right side, which fit perfectly. This bike had been running a few months before, but Mike complained that the bike had “over-heated,” during a summer parade ride and hadn’t run properly since.

The compression was a little low on the left side, so a valve adjustment was performed and there were several tight valves that needed to be adjusted. Afterward, the compression readings pretty much matched up to each other, so that alleviated having to tear down the motor for valve work or maybe tired rings. I injected grease into both bikes' grease fittings for the clutch lifters, which lessened the clutch pull quite a bit.

This bike had a Chinese-made Tytronic e-ignition plate installed, but the magnet alignments seemed to be off-target. The system is supposed to have a tiny LED light that turns ON and OFF when the timing marks are aligned, but the light had failed to function. The only way to check the timing was with a dynamic timing light with the engine running. The rotor runs in oil on these engines so they tend to spit out oil when the cover is off, but that was the only way to confirm the correct timing of the unit. It took about three tries, but finally, I saw the correct alignment of the marks, so closed it up, drained the oil and refilled it with fresh 10-30 Honda GN4 oil.

The bike got a new AGM battery installed, as its original AGM was robbed for the gold bike. The carb bowls looked clean and the idle jets were properly sized. When run off of a separate fuel bottle, the engine started up quickly and settled down once it warmed up a bit. A test ride went well going downhill but on the return run, it faltered as if it was either seizing or running out of fuel. After switching to reserve and waiting for a moment, the engine caught back on and got me back home again. As I inspected the gas cap, I noticed that it was some kind of aftermarket cap with an edge vent hole that seemed to be pinched off during assembly. I switched to a known good cap and rode the bike for another 20 minutes without incident.

That bike had both of its original tires replaced with some Michelin City scooter tires, which are one of the few options in the correct tire sizes. The tire sizes for the CB175 are the same as specified for the 305cc CB72-77 Super Hawks, which have seventy-five more pounds of weight and 50% more horsepower. When I checked local motorcycle dealerships for some inner tubes, none of them carried anything smaller than 3.50×18.” How times have changed…

Bill Silver aka MrHonda

12/2021

What? Not again… another CB77 rescue

The past few months, it seems that all the local lame and wounded vintage Hondas have found their way to my little messy shop for repair and rejuvenation. Having been embroiled in a pair of “beach bike” CB350s, suddenly a sad, but salvageable later-model CB77 pops on Facebook forums as a project bike with a seriously seized engine. Seller was taking offers and finally settled on mine. All I had to do is drive 150 miles up the road to fetch it and bring home the remains for revival. Very few CB77s have shown up in SoCal in the past year, so I guess you have to go out and haul them in if you want to own one again.

I already have my low-budget 1963 CB77, which was a bike I pieced together 6-7 years ago, then let it go to a woman who lost her garage space and sold it to her girlfriend. She rode it out to Joshua Tree from San Diego on a woman’s ride, making the journey safely, but the bike was seeping oil out of the tachometer cable seal and she parked it in 2016. I wound up buying it back and putting it back into regular service now and was happy to have it for my runs to the post office and local trips.

Over the past year or so, I have snagged bits and pieces of Super Hawks, either to keep for emergencies or to put a little stash together in case a bike like this new one shows up for repairs. I have collected a kickstarter cover, cylinders, cylinder heads, valves, wiring harness and NOS ignition switch along with a lot of other little tidbits. So, now it looks like they will be put into play for the latest project.

The pickup adventure…

Leaving at 8:30 AM gave me about 3 hours to cover 150 miles up to and beyond LA. Waze GPS app took me off the I-5 once, across the 91W to the 605N, then back to the I-5 again. I have learned to trust it and sure enough, the bulk of the journey north went smoothly and I was there in 3 hours flat.

I gave the bike a quick once-over, noting that the cylinders were full of rust and the tank had stalactites inside once the cap was removed. It would appear that the cap was left off and the bike left outside to collect rainwater, which flowed into the open petcock, filled the carburetor bowls, then traveled down the right side cylinder’s open intake valve.

The bike only had 12k miles showing and was a 18K series 1965 model with an array of little mods including chromed fenders (front one chopped off), chromed side covers, transmission cover, footpegs and horn cover. The bike did have OEM exhaust pipes, but one muffler looked rusted out on the inside, also on the right side.

We loaded it up, I left a copy of my Classic Honda Motorcycles for Dave and the shop guys and hit the highway once again. The return leg had me headed down the I-5, then east on the I-10, then down the 710, then back to the I-5 again. In the end, the Tacoma covered 340 miles in 6.15 hours getting 26.4 mpg on the way as we tooled down the highway at 80 mph for much of the return trip.

Once the bike was unloaded, I hauled the engine up on the workbench and filled the cylinders first with Metal Rescue and Kroil, but switched to straight Metal Prep (phosphoric acid) after trying to loosen the pistons with my little steering wheel puller (as a pusher) tool attempt.

                                                           How it started out...

The next day…

Popping the float bowls off the carburetors revealed massive amounts of water damage corrosion to both carbs and the petcock. Metal was etched away on one carb main jet holder area and the petcock had a pinhole at the top where the metal had been eaten away. Fortunately, I had a spare set of square bowl carburetor bodies that should be good enough to bring the bike back to life again, once everything is put back together.

I ordered $100 worth of bits from 4into1.com and a new AGM MotoBatt battery from an eBay supplier.

I filled the gas tank with ¾ gallon of Metal Prep, let it sit for awhile then added water to the top opening and will let it sit for a few days. Hopefully, the pistons will loosen up and I can continue with the engine rebuild without resorting to violence on the piston crowns.

The worst one ever…

Using my steering wheel puller tool as a piston pusher, the pistons refused to budge, especially the left side one which was near TDC. The right side finally moved slightly, which just raised the cylinders off the crankcases ever so slightly. More pressure on the left side resulted in a loud crack and the top of the cylinder liner snapped off. The liner/piston combo could only go down so far before hitting the crankshaft, so this strategy wasn’t really working out. All I could do was totally destroy the cylinder block in order to remove the pistons from the crankshaft.

First, I took a hacksaw and sawed the cylinder block in half through the camchain cavity. Then, I had to pull the whole bottom end off the bench and over to my air compressor where I used an air chisel to pound out the right side piston from the sleeve. Next, the left side sleeve was pushed off the cylinder casting, leaving it intact and hanging from the connecting rod. I gathered it back up and put it back on the workbench, then attacked the sleeve with a Dremel tool with a cutoff wheel(s). Cutting down both sides of the sleeve about halfway allowed me to split the sleeve with a chisel, revealing a fully rusted piston from top to bottom and rust below the piston in the sleeve as well. I have never seen so much corrosion buildup between the piston and sleeve on a water-seized engine before.

The piston was finally clear of the cylinder sleeve, but we weren’t done just yet! Using a very big piston pin pusher tool, the pin was stubbornly stuck in the piston pin bores. I had to break out the Dremel tool again and cut the piston apart through the pin bore which finally relaxed enough to release the pin and the rest of the piston. I figure that it took about 6 hours of labor just to remove the pistons and cylinders from the crankcase and crankshaft. Worst one ever….

The cylinder head combustion chamber on the right side was pitted from years of standing water on that side, so it went to the scrap heap, as well. I continued to dismantle the rest of the engine in order to clean out all the debris from the piston removal process and check over the transmission and kickstarter parts. Fortunately, the bottom end was pretty clean and just needed a lot of washing of parts in order to clear the leftovers from the piston destruction process.

The whole outside of the engine was covered in layers of grease, dirt, oil, corrosion that took plenty of time just to scrape off the worst of it. I discovered a local shop that had a vapor blaster machine and was willing to clean the parts properly. Everything came back looking like fresh alloy, but needed a second cleaning/rinsing to clear leftover glass bead debris from the cleaning process. Now I could start to rebuild the engine using nice clean parts.

The spare cylinder head had good seats for the valves, only needing a little pass with the valve seat cutters to make nice shiny little circles in the cast-iron skull that comprises the combustion chamber, valve seats and spark plug hole. I installed a new set of valves with the original valve springs which had blue paint on the ends, which I had never noticed before on CB engines.

The spare cylinders on hand were still at STD bore, but one side had a single scratch down the side, but below the top couple of inches of piston travel. I cleaned up a set of STD pistons and rings that were hiding in a box and set about putting the whole top end back together with replacement parts from stock. The bottom end really didn’t need much in the way of replacements, apart from the kickstarter pawl which was somewhat rounded off on the contact surface.

Reassembly of these engines takes more time than you would expect, especially when each part needs to be cleaned and evaluated for re-use. I spent a couple of afternoons cleaning and assembling all the bits and pieces until I had a gleaming shiny engine assembly sitting on the bench. Next step, the chassis..

I spent a good part of a day first removing the front wheel and forks in order to replace the left side upper fork ear, which was flattened out from some impact. I was able to get a NOS part from www.davidsilverspares.com for $65, which came in factory primer, so needed a coat of black paint to match the rest of the bike. While apart, I cleaned the fork seal holders and the chromed trim rings which had some pitting, but were good enough for the moment.

Invariably, the brake cams on these bikes are all sticky from 50-year-old grease and the intrusion of moisture over the years, so they must be dismantled, cleaned and lubricated. Honda didn’t make it very easy to dismantle the brake plates, as the brake shoe pivot bolts are held into the plate with nuts on the outside which have little punch mark stakes in two places. There is no room to get a socket onto the nuts, so I went in from the backside and used an air tool to break the 19mm head bolts loose from the 17mm nuts on the outside. Once apart, I replaced the front shoes with new aftermarket Vesrah brand replacements, which are non-asbestos materials. The original 5mm shoe thickness was worn down to about 4.3mm on the front and 3.4mm on the rears. I wound up using the used front shoes on the rear brakes in the end.

Both brake drums were rusted, as expected, but a half hour of cleaning with a drill motor and small wire wheel eventually removes all the rust and scale from the drums. More time was spent cleaning the rims with 0000 steel wool, just to make them look a little more presentable. The whole bike was just dirty and corroded to a degree, but Honda’s chrome was of pretty good quality and a lot of the original finishes came back up pretty well.

The bobbed front fender, which had been chromed was a problem to solve. I discovered an eBay vendor who had some of the Japanese made replacement fenders which I have seen before on other bikes in the past. The front fenders on CBs come in two versions, depending upon how they mount to the forks. This early bike has the steel fork sliders, so needs the early hockey stick type of center mounting ears. I knew that it wasn’t really the best option but at $100 it seemed like a good temporary fix for the front fender situation. The fender arrived quickly, but the troubles were just beginning.

For all appearances, the fender should have bolted up to the forks, as planned, but when the locating pins were pushed into the fender stay pads, the bolt holes were off about half a hole diameter. Well, that was weird, but perhaps they just had a bad day at the factory back then, I thought. Unfortunately, the more I whittled on the fender mounting hardware, the more it seemed like this was really NOT designed for this bike! The fender sits up about 2” above the tire and neither of the fender stays come within 2” of connecting to the fork slider. The curvature seems a little off, as well, perhaps due to the possibility that the fender was designed for a 19” wheel not the 18” wheel of a CB77. So, I really don’t know what this fender was destined for but it doesn’t appear to be for a Super Hawk model. The only other fender of that type of mounting system is the early CB450K0 Black Bombers, but I was never aware that there were aftermarket fenders designed for that model. So, no I am stuck with an ugly $100 fender that doesn’t work at all on this bike and is so carved up that it can’t be returned now. Interesting lesson learned here…

Next up, the marriage…

The chassis needed a good scrubbing to clear off years of dirt, oil and corrosion, so it got a good bath before the engine was reinstalled into its original place. Once cleaned off, there are still many hours of work to do in order to make this machine come back to life again.

As in interesting sidelight, the guy who did my vapor blasting had a black CB77 rolling chassis with motor sitting on a second level floor, just kind of hanging out there. It had a seat and fuel tank, which I needed for the LA bike, so I asked about it. The owner said, “You sold me that bike for $100 years ago and you can have it back for $100.” So, I added $100 to the bill and brought back yet another CB77 to make it a trio at the house for now.

Fired up, but leaking oil…

The engine started up on the first few turns, coughing and smoking out the mufflers for a few minutes. A few oil drips showed up quickly on both cylinder head covers, probably due to my reuse of the parts that still had the original gaskets. They looked good enough to reuse, but they were hard and just didn’t seal well. I replaced both cover gaskets, which cured the oil leaks there, but a more serious one materialized at the middle of the brand new head gasket. The head gasket was from an aftermarket company with little dimples across the surfaces. I don’t know what happened there, but it was disappointing to see and required another engine removal to replace the gasket and check the o-rings for sealing. The o-rings are supposed to be 2mm thick, but some of the aftermarket versions seem to be closer to 1.75mm. Digging into a Harbor Freight box of Viton o-rings, I came up with some that were about 2.4mm thick, so I opted to use those instead. I also coated the inside of the o-ring holes in the head gasket with some liquid sealer to prevent oil migration laterally through the gasket material. I coated the gasket with Gasket-Cinch and let it set up before installing the gasket and cylinder head.

Using a hydraulic bike lift to help handle the engine assembly made it a bit easier on my aging spine, but I still have to lift it up/down about a foot from the bench to the lift. I always feel it the next day or two, though. It winds up being a good 3-4 hour job to manually dismantle the bike’s external parts and ease the motor down and out of the frame. A good hour or so was spent on the bench, dismantling the cylinder head from the engine and cleaning, inspecting, gasket scraping, and prepping the parts for reassembly. Then, it is back onto the lift and back over to the frame. Unlike the Scramblers, the Super Hawk engines go straight up into the frame from the bottom, so jockeying it around and into the mounting points is much less of a strain on the old bones.

Fired up 2.0...

Once the bike was nearly back together again, the engine was test-fired to verify that the head gasket leak was solved and everything was back to specs again. For almost all of the CB77s that have come my way, I have installed #140 main jets to compensate for the alcohol in today’s fuel supplies. This setup in my 1963 CB77 works flawlessly, with easy cold starts and smooth fuel delivery all the way to redline. This 1965 bike wasn’t having any of that...

First, the bike sounded like it was running very rich at mid-range and spitting back through the left carburetor off-idle, which is a confusing combination of symptoms. I discovered that once the fuel tank was cinched down onto the frame, apparently the throttle cable was getting pinched off somehow and the carb synch was WAY OFF. The left side was lifting 1/4” before the right side started up. It wasn’t making much sense as the new cable was used and the carb slides and adjusters were matching height at first. When the fuel tank was loosened up, the carb synch issues swapped sides! Pushing the parts around finally got the cables to match up normally and the carb synch was restored. I had installed a set of OEM carb needles and have moved the needle clips up and down, trying to find the happy place for the engine.

Finally, I swapped out the #140 mains for a set of stock #135s and the engine began to smooth out through the rev range. The ignition timing was rechecked using an automotive timing light and it was discovered that when both sides were setup at the F mark at idle, the wear inside of the camsprocket advancer weight pads have compressed somewhat which creates excessive spark timing at full advance. I have found that you MUST contain the spark advance to stay close to the II marks on the rotor at full advance. Setting the spark advance timing to that limit yielded idle spark timing at the T mark instead of the F mark.

My friend Tim Miller, down in TX, dismantles the camsprockets and modifies the spark advance curves so that they have about 10 degrees less total timing advance, but this allows the engines to run about 10 degrees BTDC at idle, which is where they really like to be. If the engine has to come down again in the future, I will ship the camsprocket out to Tim for rebuilding.

A few local test rides are showing promise as the engine beds in and the carbon and oil is all burned out of the exhaust system. The engine compression readings are right at 160 psi on both sides, which is about normal for the later lower compression piston setups that Honda used after 1965.

Some of the big-ticket items for this revival included nearly $400 just for vapor blasting the engine components, $65 for the AGM battery, then another $50 just for the battery hold-down plate and cushion, $60 for a new drive chain, $65 for a set of mirrors, $155 for a set of cables to replace the original tach, speedo, clutch, front brake, rear brake and throttle units. I used the gas tank from the newly acquired $100 parts bike, which needed a $160 clean and seal, then a $125 black paint job. I added one of my little Dream 50 tail light lenses, which are an inch and a half shorter than the regular long lens used on all of the 1963-66 models. The stock right-side muffler had a section that was rusted through in one spot which required a $50 welding job. The speedometer went haywire on the first drive, so $275 was spent on getting the meters rebuilt at Foreign Speedometer here in San Diego. I picked up an aftermarket blue seat from my friend in TN who brought it to the Barber Vintage Festival in Oct. $90 including shipping back to San Diego. The original seat pan was poorly repaired with someone with an arc welder, instead of a TIG welder. Aftermarket copy seat bolts set me back another $20.

The spare cylinder head got a new set of valves which run about $100, then gaskets and seals add another $80 to the mix. I already had a spare set of cylinders, STD pistons/rings that were used but good enough to put together with confidence. The head and cylinders/pistons would have run another $250 if I had to purchase them elsewhere. Tim McDowell supplied a set of aftermarket air filters, air tubes speedometer packing, and other bits that ran up another $200. The carburetors needed kit parts and floats, so $80 more to the total. The new CA title costs $55 plus 2 trips to DMV and one to CHP offices for inspection and VIN verification appointments. After awhile, you step back and gasp at all of the money spent just to get a bike like this from parts bike status to a full running motorcycle again. The parts bills can easily run to $2k especially if you have to buy new pistons/rings and then bore the cylinders for $90 to machine two cylinders. And don’t ask about the hours invested in all the steps to clean, repair and assemble the whole bike again…

In the process of rebuilding the bike, which still has the original paint and all of the extra chromed parts attached, the former owner of my 1963 bike (which I bought back from her a few months ago) fed me a referral to an interested buyer for the 1965 bike. He brought his 12-year-old son with him and even though the bike wasn’t quite finished, then had a flat tire, but he was enamored with it and wished to buy it when everything is complete.

So, in less than 2 months, the very dead CB77 is now back on its wheels, with a running, rebuilt engine and a promising future with a new family who plan to keep it as an heirloom to be passed down to the next generation in years to come. The end result makes all the labor and expenses worthwhile.

                                                                   THE END...

Bill “MrHonda” Silver

11/2021

Pretty CL77 Scrambler with a dark secret…

A recent request from an LA-based owner of a CL77 lead to the next big adventure in vintage Honda repairs. The bike had been “restored” by an owner in WA state and posted on Craigslist for sale. The current owner, Mike, had picked it up while visiting his daughter not far away from where the bike was listed, so he went to see it. The bike was not running at the time and the apparently motivated seller sold it for a very cheap price. The bike had been restored with new chrome on the rims and exhaust, new paint on the bodywork and everything looked pretty tidy overall when it arrived on the back of a trailer to Casa de Honda for a “get running” request. I figured that I would just troubleshoot it, fix it and turn him back around to LA within an hour or two…

First step on an unknown bike is to check compression readings. The left side came up at 175 psi, but the right side died off at 60 psi. Not a good start for the day… Next step was to check for tight valves on that side, but when it was brought up to TDC compression, it was evident that there was normal valve clearances on both valves. My little portable bore-scope revealed a coating of carbon on the piston crown and signs of dished valve faces, which seems pretty prevalent these days.

The main issues that kept the bike from starting up were both idle/pilot jets were plugged up and the float levels were at 26mm not 22.5mm. Wrestling with carb jets on a Scrambler are always challenging, especially on the left side near the exhaust system and the oil filler tube. After contorting myself in various ways in order to access the idle jets and reset the floats, I finally got it to a point where it should fire up, all things considered. I checked the ignition timing statically and it was within a few degrees of normal and the points were opening and closing properly. Two kicks and the engine fired right up, filling the neighborhood with the distinctive sound of straight-pipe 305 Scrambler noises.

Unfortunately, the running engine was blowing out clouds of blue smoke out of the breather hose in vast volumes, indicating bad rings, scored cylinder walls or worse. It was time to tear it down and see what had happened to the engine. After unbolting the engine and wrestling it out of the chassis, the truth was about to be revealed on the workbench.

It appeared that the engine had been lightly sandblasted and painted with a light aluminum paint. When the kickstarter cover was removed all the sandy flakes were packed around the rotor and countershaft sprocket area. So, pretty on the outside, but not really cared for beneath the surface.

The engine top cover was removed and checked to see if the breather holes on the plate were oriented properly. If the breather plate holes are installed at the top of the head, then oil gets trapped and blown out of the breather tube. There are arrows on the plate to indicate that the holes should be positioned down/forward, but I suppose you could interpret it as the arrows indicating TOP/UP instead. Anyway, they had been installed correctly, so that was not a contributing factor.

Once the cylinder had nuts were removed beneath the spark plugs, the head slid right off the studs revealing a surprise. The right side piston had a small section melted away from detonation, which extended all the way through the ring pack. Further more, the head gasket fire ring was blown through towards the camchain cavity, so the reasons for all the smoke were quite evident now.

The cylinder bores showed signs of water/corrosion damage in the past, plus there was a chunk of melted aluminum clinging to the top edge of the right side cylinder bore. The pistons were still on STD bore size, but the condition of the bores required over-sized pistons and a rebore to fit them. That lead to the next challenge which was to find some correct pistons and rings at a reasonable price. Ebay sellers were asking anywhere from $50 a piston to $150, with a full set of pistons and rings running from $250 to $400 a pair. My friend Tim McDowell at www.classichondarestorations.com is the distributor for WISECO forged pistons to fit the 305s, but was out of stock and the manufacturer was waiting for piston blanks that were probably on one of the thousands of container ships that were sitting offshore waiting for their turn at the end of the 2021 season. A somewhat reasonable option were IMD piston kits that were engineered in the UK but made in Taiwan. At $169 a set they seemed to be a good option including the 3 piece oil rings that come with modern designed parts. The puzzling part of these piston offerings were that they chose to use the lower compression Dream piston crown configurations rather than the standard higher compression CB series shapes.

I have built up CB engines with Dream pistons, due to lack of proper piston options and they still work fine, but have a bit lower compression readings in the end. This engine was not going to be raced in competition or ridden extensively on the highway according to the owner, so putting the engine together with IMD pistons was the wise option in the moment.

I noticed that when the pistons were removed from the rods, turning the engine over with the rotor left a feeling that something was causing excessive friction on the crankshaft. Rolling the engine over on the bench to remove the clutch cover revealed that the oil filter was stuck on the shaft and the outside cover had been hammered onto the shaft end with the locating pin out of position. This condition was holding the cover just back from fully sealing up the cover to prevent oil drips which were evident as the bike was initially parked.

The oil filter thrust washer had been placed on the inside of the shaft next to the crankcase, which pushes the oil filter chain off-center. This causes side wear on the little filter chain sprocket teeth. Once the filter shaft as extracted from the outer cover and the filter removed from the shaft, the filter was cleaned out of the 1/8” of accumulated grit and debris that the filter had accumulated over the last 50 years.

The cylinder head was dismantled, apart from the cams, so the valves could be removed and inspected. The exhaust seats had a lot of little depression marks and the intakes were quite wide and rounded. All the valves were replaced, with seats re-cut and narrowed to meet up with fresh 45 degree angled valve faces.

As always, considerable time is expended in removing the old, caked-on gaskets from the alloy surfaces without digging into the metal too often. I have found that it usually takes between 1 and 2 hours to successfully clean all the gasket surfaces, particularly on bikes with the original asbestos gasket material.

While awaiting the arrival of a set of pistons to send to the machine shop, any other loose ends must be addressed, which in this case was some kind of solid-state full-wave rectifier cube that had been loosely fitted to the chassis and found to be un-grounded when the engine was removed.

Taking a turn for the worse…

In setting the cylinder block down into a cardboard box for transport to the machine shop, I was shocked to see the right side liner just pop up all by itself. I lifted the cylinders up and grabbed the liner with my hand and it just moved up and down and turned either way easily. This is NOT a good sign. Normally, the liners need a little time in a low-temp oven in order to get them extracted from the cylinder casting. Chilling the liners and heating the cylinder block is the usual way to re-install the liners once again. I called the machine shop and told the owner what the situation was. He said to bring it all in and let him evaluate the situation. His call-back revealed an approximate clearance between the right sleeve and cylinder block at .004” which is not the desired interference fit expected. After washing the parts off in his steam cabinet the other sleeve came out with little effort. After careful measuring, he decided to swap sleeves in the block which ended up with about .002” clearance. He lathered up the sleeves with Red Loctite and let them sit overnight to let the adhesive setup and cure fully. Once he sets the cylinders up in the boring bar, the results will become evident; either the cylinders bore out normally, or the liners break loose and start spinning in the cylinder block which signals the end of the usefulness of this set of cylinders.

Results…

The machinist called to say the cylinders were ready and they turned out fine. I made the 25 mile round trip to pick them up and cart them home for installation. The top end was reassembled in an hour or so, then I dragged the big lump off the bench and onto a cart where it met up with the chassis. Some soft rags were taped to the frame to minimize paint damage as the engine was wedged back into the chassis. Scramblers continue to be the most challenging bikes to service and to do big jobs on as far as I am concerned. After another hour plus, it was time to light it off…

Good news, bad news…

The bike started on the 3^rd kick, but sounded like a top fuel drag car; a combination of straight exhaust pipes and a bunch of other issues that arose. When the carbs were reinstalled the right side throttle cable adjuster was a 1/4” higher than the other side for reasons unknown. This caused the right side to be pulling the other side along under load, which adds to the stress and overheating of the cylinder. The carb float levels were re-checked before installation and the jetting was all stock. There was no immediately apparent reason for excess fueling of the engine, but the air screws didn’t have any affect on the idle richness.

The spark timing was set for the left side which ran up to the II advancer marks properly. The right side timing was way off at idle and when it was retarded back to the F mark, the engine died a few times, but was noted to exceed the advancer marks by a good 10 degrees, which would certainly cause overheating and seizures under load. After the spark plugs loaded up with black carbon it was time to call it a day and consider all of the possibilities for this suprising outcome. The good news is that the cylinder pressure with the new pistons was 175-180psi on both sides.

Back to basics…

With fresh eyes and better daylight, the re-check commenced. The point brand was verified as genuine ND (Nippon Denso), but someone had replaced the original screws and washers with mushroom head screws that tend to move the point base around as you tighten the screws. The point gap was opened up a little past the .016” to ensure that both sets were not closed momentarily causing a voltage drop to the coils. The ignition timing was set statically with a 12v test light and eventually verified with the engine running to ensure that there were no over-advancing problems with spark timing which causes piston seizures and detonation holes. One step done…

Next, the carburetors were removed again to check the air bleed passages going to the idle and main jet circuits. They were clear, but the emulsion tube holes for the main jet holder were contaminated with some leftover corrosion due to old gas left in the carbs. The float levels were double-checked, the floats tested for any pinholes which leads to sinking of the floats. All the jets were stock Honda, but the carb slide needles were not marked, which is usually due to the originals being replaced by aftermarket Keyster carb parts. I sifted through about 20 needles in a bin and found an actual OEM CL77 needle, plus a Keyster D13 replacement needle. The idle jets were cleaned previously which got the bike to start up, but eventually, the #38 idle jets were replaced with #35 spares to lessen the rich idle condition.

The new needles were attached to the carb slides and the two slides were inserted into the carb bodies.

The sooted-up spark plugs were replaced with a fresh set of D8HA NGK plugs and the bike seemed to finally get its feet again. The air filter and side cover were reattached to the bike chassis before the pipes were installed again.

The bike had been running on a temporary fuel source. Once the engine sounded healthy again, the fuel tank was reinstalled and refilled. I have learned to always check the air pressure before a test ride and sure enough, I was looking at tire pressures of 15 upfront and near zero for the rear. Finally, with everything attached, I ventured out for a quick run about a half-mile away on a road where there are few houses and listening ears to be offended/treated by the sound of a straight-pipe Honda 305 Scrambler.

The rear tail light wasn’t working which was traced down to lacking a good ground from the tail light to the bracket to the rear fender, which is a common problem when freshly painted or powdercoated body parts are reinstalled without consideration of the need for a solid ground path for the electricity. I failed to check the neutral switch condition when the engine was reinstalled and sure enough, it appears to be the source of the non-working neutral light circuit. Checking it requires removal of the footpeg assembly and removal of the kickstarter cover to access the switch and connections. Just when you think you have it done… there’s always something left to do.

I did manage to address the last electrical issues while I waited for the arrival of the owner, who made the trip back down from LA to retrieve his prize CL77. The neutral switch pigtail wire had become unsoldered and the incomplete ground path for the tail light was cleaned and reconnected so that all the lighting systems were once again functional.

The owner took the bike for a quick blast around the neighborhood and rolled it up into his bike trailer for the return trip back home again. It was a far cry from “I can’t get it started” to “Please fix it and let me know when it is done.” These old bikes are full of surprises and this one presented problems not previously seen before. In the end, it lives and breathes again to the delight of the happy owner.

Bill “MrHonda” Silver

11/2021

Know when to say “NO!”

Having owned somewhere around 400 cars and mostly Honda motorcycles in the past 55 years, I seldom pass on an opportunity to pick up a vintage 1960s Honda motorcycle, especially a CB77 Super Hawk. A recent Craigslist posting was shared with me by my friend Burt, who had just seen it a few hours after it was listed.

1963 Honda 305 superhawk parts bike - $300 (Lakeside) needs restoration, mostly complete.

Burt sent my phone number to the seller who called back promptly and answered a few questions including the serial numbers which did match up to a 1963 CB77. Based upon his evaluation and answers to my questions, I packed up the Tacoma and headed out to the location, just 20 minutes away from home, hoping to find some good spares for my already running and riding 1963 CB77. I had put the bike together about 7 years ago from a pile of parts, powder-coating the whole thing black which was cheap and easy. After a 2 hour struggle, I was able to remove the pistons and complete an engine rebuild successfully. The bike was sold to a friend who sold it to her friend, then it went into storage in 2017. I bought it back, revived it, and have used it weekly as a post office box runner, but it could use a bit of bling here and there and a revised seat.

Arriving at the seller’s residence, they remarked that they owned a twin to my silver Tacoma, except theirs had 235k miles and mine 63k. The bike was sitting up on a dirt bank with 2 flat tires and both wheels locked up from rust. The drive chain was rusted solid and the front brake arms would not budge even with a plastic dead blow hammer. The tank had been left without a cap for a long time and there was no petcock. The seat pan had blue upholstery and the original outside strap buckle hardware rusted in place. The ignition switch was broken away from the key section and the left side cover knob seemed to be cemented firmly in place. The horn was missing, the speedo-tach broken and faded and even the dimmer switch functions were all frozen in place.

The bike had been painted metallic green, the rear fender replaced with a custom piece and of course, the big pull-back handlebars were all signs of a “customizing” job common in the 1960s-70s. I stared at the bike’s details for probably 15 minutes, trying to find some redeeming qualities that would make me want to drag it (literally) home, but apart from the chrome-plated factory side stand and perhaps being able to save the fuel tank, there was so much rust on every surface that it would take gallons of Metal Rescue to just get it dismantled and then refinish every surface.

I offered $200 but the seller’s wife said that her husband was “firm” on the price, so I picked up my hammer and left quietly. It’s hard to know who might pay that amount for a bike in that condition, but I guess someone will eventually haul it away. Having dismantled more than a few CB77s in that condition, I have decided that that is not the best use of my time and dollars anymore. I had to pat myself on the back for walking away from this one, as it is a rare occurrence when I do. There are times when the wise thing is to know when to say NO, and mean it.

Bill Silver

aka MrHonda 8/2021

Trouble-shooting the early vintage Hondas…

I am on several forums dedicated to vintage Honda motorcycles and see a lot of similar questions and complaints about various aspects of owning and reviving these 50-60-year-old machines. I thought I would go over some of the basics once again for newbies that are just getting into the hobby. So, let’s start at the beginning… You bought it and now… See * at the bottom of the story first.

1.

It won’t start… Does it turn over and feel like there is some compression being built up in the cylinder (s)? Test compression first, even if you don’t have a gauge. Put your fingertip in the spark plug hole and turn the engine over, however you can at the same time. Holding the throttle wide open gives the best results. If you do have a gauge, it should be reading anything from 125 to 180psi. If you are looking at 75-90psi, it won’t start and run at all. Try adjusting the valves first to see if they are leaking compression past the valve heads/seats. If that doesn’t help then it is time to pull the head/engine and find out if the valves are tight/burned or the piston is scored/broken from seizures in the past.

2.

It turns over AND has compression… Does it have spark at the spark plug? Determine if the bike requires a battery or if it has a magneto (mostly 50-80cc singles). A bike with a magneto ignition system doesn’t need a battery to make the coil spark, but if you start up a bike that has a battery in it for the lights and horn and the battery is dead, any light bulb that is normally lit will be blown out from the uncontrolled charging system output.

3.

For bikes with battery-powered ignition systems, you MUST put in a fully-charged battery to make the engine run. If you jump-start a dead/dying battery enough to get the engine to run, the light bulbs are also at risk. Most Hondas of that era do not have voltage regulators, preferring to use the fully-charged battery as a buffer to absorb the charging system output and prevent over-voltage situations.

4.

So… now you have compression and spark, perhaps, but does the spark come at the right time? The ignition points are basically just variable electrical switches. Setting the point gap at the highest spot on the point cam is the starting point of the ignition timing exercise. Also, the point’s contact faces must be clean and shiny to maximize the spark energy in the coil. So, set the gap at around .012-.016” and then ensure that the points are closing together and making clean contact with each other. If the point faces show a > > instead of | | contact pattern then the condensers should be replaced. Bad condensers also cause a lot of visible arcing across the point gap when the engine is running. BEWARE of any aftermarket copies of the original Nippon Denso, Hitachi, Kokusan, TEK and other OEM point sets. Many copies have incorrect dimensions for the point rubbing blocks and setting the ignition timing is nearly impossible. Daiichi, SEV, Century and other brands are not recommended. OEM points will have ND or a different symbol for Hitachi and Kokusan stamped on the point bases.

5.

Ignition timing is set by the points just opening at the F (firing) mark. Moving the backing plate back and forth will help you to dial in the correct ignition timing. On some twins, you have to set the left side points to the normal gap, move the backing plate to where they open on the LF mark, then you will have to change the right side point gap open/close until those points open at the F mark.

6.

Once you are sure that the ignition system is setup properly to start the engine, then you have to determine if the mechanical spark advancer is doing its advance/retard function properly. Point cams can get hung up on rust or old grease on the cam base plate shaft and that will alter how the spark timing occurs. If the point cam is slow to return to full retard at idle, then remove, mark and clean the point base shaft and the point cam, so that they both move easily back and forth. Use special point cam grease on the point cam to reduce excess rubbing and friction during operation.

7.

So, if your compression and spark timing are all correct, then it is onto the fuel system for cleaning and testing for full function. For carburetors which have been left standing with old fuels in the float bowl for months/years, the chances of the bike starting normally are very slim. For the engine to start up the idle jet must be clear and the adjacent air bleed ports in the carburetor throat must be open.

The carburetor float chamber must have the correct level of clean, fresh fuel in order to feed the idle and power/main jet circuits. Each carburetor has a specific float level adjustment which must be adhered to for proper operation. Also, there are air bleed ports in the carburetor inlet that must be clean for proper fuel mixing. Also, be sure that the bowl vent passages in the roof of the carb body are open.

If the carburetor needs to be cleaned, use an ultrasound machine to clean out the small passages of the carburetor body and any removed OEM parts. In many cases, the aftermarket carb kits are not accurately made, so try to use as many of the original parts as possible during reassembly.

Yesterday’s carburetors are deeply affected by today’s fuels, which are generally loaded up with 10% alcohol to reduce emissions and stretch out the fuel supplies. Because the fuel is somewhat diluted, there is less energy released when the fuel vapors burn. This situation creates a lean ratio mixture condition that generally needs to be corrected with larger-sized jets, at least for the main jet circuits.

You must check all the carburetor components carefully as they can be damaged by the old fuel vapors and solids that remain inside the float bowl after months or years of neglect Most older carburetors used small brass floats which can be compromised by the acids in old fuels which etch into the metal and create pinholes. These tiny holes will allow gasoline to enter the float lobes causing them to lose buoyancy and start to sink into the float bowl. When that occurs the float cannot control the fuel level in the bowl, which creates an overflow condition.

When fuel flows out of the overflow tubes at the bottom of the bowl, you have problems with either the float valve not shutting off or the float itself. Figure out which is at fault and repair it before moving forward with the startup cycle. If you are sure that the float level is set correctly and the float valve is doing its job, then look carefully at the overflow tube in the float bowl. They have a tendency to split along the lengths of them, causing persistent fuel leaks at the tube exit.

8.

When setting up the carburetor body, install the idle mixture screw and back it out about 1-1/2 turns to begin with. Turn the idle speed screw in until it contacts the bottom of the slide and just starts to raise it upwards. Be aware that idle screws come in two functions: Air screws and fuel screws. When you back out an air screw, more air is added to the idle mixture. When you back out the needle-like fuel screws, more gasoline is added to the mixture. For carburetors that bolt onto the back of the cylinder head, look for warped flanges and flattened out o-rings that seal the carb to the insulator, which seals to the cylinder head. Insulators will either be sealed with an o-ring or a flat gasket.

Obviously, if you are working on a twin or four-cylinder model, your work will be multiplied and you will have to make sure that the carburetors are synchronized properly on all cylinders. Twin-cylinder bikes can be synchronized by watching the slides lift off of the idle speed screws. To begin, turn the speed screws in until you see the slides just begin to lift. Then, adjust the cables at the top of the carburetor using the screw adjusters. For 350-450 CV carbs, you will have to watch both of the carburetor cable arms to ensure that they both move at the same time. REMEMBER: For twins with standard slide-type carburetors the slides are side-specific. You must see the slide bottom cutaways in the throat of the carburetor. They must always face the air filters. If you reverse the slides, you will get fouled spark plugs and a very high idle when you start the engine. Yes, they will install backward!

Fuel: When the 1960-70s bikes were built, fuel quality was much higher in octane ratings. Regular fuel was 90 something octane and premium fuel was 100-105 octane and all of it contained lead to protect the valve seats. Unless you are buying your gas at a boat marina, airport or from a race gas station, you will have to deal with the usual 10% alcohol infusion with octane ratings of 87/89/92. Gasoline chemistry has changed radically in the last century and the octane ratings used in the last century are not necessarily a match for today’s fuel ratings. My rule of thumb is to use premium fuel for vintage Hondas, either with or without alcohol. What I have discovered is that with alcohol-infused fuels, the engines run leaner and often need a 5-10% increase in the main jet sizes to compensate for the alcohol additives in today’s fuels. My recent experience is that most CB77 Super Hawks run best on a #140 main jet vs. the stock #135 main jets specified from the factory. If your machine is tuned to full normal specs and is still giving performance problems, try stepping the main jet up a size or two.

*Of course, always start the process by checking to see if the engine has enough oil to meet the marks on the dipstick. Low oil levels can often lead to seized and damaged engine parts, so making sure that the engine has sufficient oil in the engine. You might want to drain and flush the engine oil FIRST before you go forward with the above steps. If chunks of metal or a lot of aluminum specks come out of the oil, there may be expensive issues going on inside the engine that won’t be helped with the above troubleshooting and tune-up steps.

If you have followed all the above steps, you should have a running motorcycle once again.

Bill Silver 8/2021

Not so nifty, Honda CL350... at least in the beginning…

The latest “get it running” project bike came in from Colorado a few years ago and had been parked here in San Diego ever since, while the owner completed law school. It was bought without getting a second opinion but apparently did run somewhat over a year period before it was moved down to CA. It is a pseudo-cafe racer machine, based upon a 1972 CL350K4. Whoever built it up used a one-piece alloy seat with tail piece and a couple of turn signal stalks poking out of the rear on both sides, like little ant antennae. The requisite removal of the rear fender sections, stock exhaust and installation of flat bars made up the majority of the modifications at first glance.

The exhaust system had heat-wrapped, low-slung CB350 header pipes connected with some tubing adapters to connect some long chromed baloney mufflers to the chassis. The owner complained of a rather loud exhaust note, so the plan was to replace the mufflers with something hopefully quieter.

Overall, the tires were dated back into the early 2000s, the drive chain was all rusted over, the fuel tank had about a gallon of very old gasoline inside that had eaten away at the old Kreme coating that was done years before. The forks were leaking badly at the seals and the engine had a line of oil leaks around the head gasket area and just below. The battery was an off-brand that was wedged into the battery box and the original airbox with filters had been replaced by K&N type pod filters. 

The handlebars were black and flat, adorned with unknown handlebar control switches and lever brackets. All the cables were either too long or very badly cracked and the rear brake adjuster nut was riding well up the brake rod threads. It was showing about 19k miles on the speedometer, which showed signs of water leaks in and around the faces. Other than that, it was great! :>)

So, the first order of business was to remove the old battery, send the fuel tank out for cleaning and recoating, overhaul the carburetors and petcock, remove the old exhaust system and eventually address the leaking fork seals.

About $600 was spent fairly quickly on new tires, tubes, drive chain, carb kits, MOTOBATT battery, petcock repair kit, new cables, and tune-up parts. The repairs progressed as the parts arrived from near and far. The tank sealing cost $165, $70 for the battery, $80 for carb and petcock kit parts including new manifolds, new spark plugs and plug caps, and fresh 5.5mm Honda fuel line.

Starting out, the first little problem area was the fact that the carburetors were not a matched pair. 3 D on one side and 722A on the other side. The stock calibrations for the carburetors were different, so one side was running leaner than the other side. The petcock was so rusted and plugged up that a whole replacement one was installed once the tank came back from the shop. I pried out the old gas cap insert and soaked it in Metal Rescue for a day or so, then installed it back with a new cap gasket that wraps around the edges of the inner cap insert.

I blocked up the bike enough to get the forks off and discovered that the stock fork seals were too small for these forks. The fork setup appeared to be from a hydraulic brake model, eventually identified as probably a CB350 Four, which used a long damper rod screwed into the top fork nut. The fender was a match to the forks with the loop for the hydraulic hose. The standard 19” CL350 front drum brake wheel assembly bolted right into the forks, however. 3.00x19 tires seem to be difficult to source these days, so a set of IRC rubber was sourced from 4into1.com that were offered as 3.25x19” front and 3.50x18” rear. With the forks apart, the issue with seal size (not stock CL350!) became apparent. I had one leftover in stock, but had to order another one from 4into1.com as there were none in Honda dealers inventories in California.

Most of the parts came in within a week, so the front tire was changed out after the forks had been rebuilt. The battery came in and the carb overhaul was completed. With power to the system and fuel in the newly relined gas tank, I tried to fire it up to actually hear it run. And it did fire up quickly, however there was a noticeable snapping/knocking sound going on inside the engine as it idled. I tried to pinpoint the source, but it was resonating around inside the engine and not easily determined at first.

I removed the dyno cover and turned the engine over slowly by hand with a wrench on the rotor bolt. At specific times, the snap noise could be heard which gave me a clue that something was happening with the cams, timing chain or valve train components. The next challenge was to remove the top engine cover without removing the whole engine assembly. Honda didn’t leave any extra room around the top of the engine enough to remove the top head cover without either dropping the engine done off of the mounting bolts or pulling it all the way out. I had run across a similar problem with a CB350 engine where just the top rocker box cover gaskets needed to be replaced. I removed the engine mounting bolts and it left me just enough room to get the cover removed. Still that was a lot of unbolting and reassembling the engine components just to get to the top cover. I considered that there might be another option…

Using a cordless drill and some drill bits and grinding bits I ground away a little section of the frame and a matching section of the top cover mount bolt boss and eventually got enough clearance to remove the cover from the engine with everything still bolted in place. You won’t find that procedure in the shop manual, however. With the cover removed, I slowly turned the engine over again with a wrench and heard the distinctive snapping noise in and around the camshaft. As I rocked the engine back and forth very slightly, I could see the camsprocket floating back and forth on the camshaft mounting bolts!

The bolts had backed out to the point where it took more than one turn to get them tightened up against the cam sprocket again. I cleaned the bolts and secured them with Loctite and reassembled everything again. A touch of the starter button had the engine running and it was smooth and quiet like a stock engine should sound. Success for the shortcut repair!

Changing the cables lead to an interesting find. Inside the clutch lifter mechanism there was a little cutoff metal tubing spacer sitting just below the #10 ball bearing. It appeared that there was a problem with the clutch pushrod clearance and that was the answer at the moment. When I installed the new cable, I just left the steel ball in where it belonged, alone, and then discovered that someone had turned the adjustment screw all the way in the wrong direction. When the adjustment was made correctly, the cable pull feel relaxed about 30% and it now felt smooth and normal whereas it was a very hard pull when the bike arrived.

The rear fender was missing so the license plate was mounted upon an aftermarket bracket with built-in LED light that mounted onto the end of the rear axle nut! In order for it to fit, the axle nut needed to be threaded on backward in order for the cotter pin holes to line up!

I finally got it out for a test drive and the overall performance seemed to be nearly faultless. It was a little bit loud but the new mufflers have a removable baffle that can be packed for further sound-deadening purposes. Thus far, the carburetors seem to be dialed in pretty well, but a plug check will let me know more about how it is doing. I have concerns about carburetors that are just hanging on the end of a short, stubby, rubber manifold instead of being supported on both ends by an airbox and filters that are attached to the chassis.

With a new set of tires installed, the centerstand wouldn’t do its job because the aftermarket shocks were about an inch too long. The quick test rides showed no speedometer function, which first led to a discovery that the aftermarket speedometer cable wouldn’t register all the way into the front hub. Trying a spare cable, then revealed that the speedometer needle would barely move up to about 20mph and the reset trip meter knob was locked up solidly. I had a NOS speedometer for a CL450 which worked perfectly after installation. In removing the old speedometer, the single instrument light socket was rusted and the bulb was defunct. I can only imagine what the inside of the old speedometer parts look like now.

Winding down the project, the installation of a set of 12.5” rear shocks solved most of the centerstand instability. As the high spots on the tires wear down a bit it will be just fine. The bike fires up quickly and is running well now. There aren’t any apparent oil leaks, so all the gunk on the front of the cylinders and head came from leaking forks.

It isn’t real pretty, but it is all dialed in and running well now. Next!

Bill “MrHonda” Silver

8/2021