In the past few weeks, another parade of lifeless motorcycles has come through the shop and each one had various unique challenges and surprises, in some cases.
This bike has been a thorn in the side of the owner and me for a year or so. The bike was only used in the summer months, so sat for long periods with a half-full tank of alcohol gas and a weak battery and charging system. After a new battery was installed, it didn’t seem to be getting a good charge, so a new solid-state reg/rectifier was tried out but was either a defective unit or just not the right type for that old school design. Putting the old parts back in carefully seemed to have awakened something and then the bike ran well for a few weeks. Then there were misfiring problems that lead to a house-call where I discovered a loose ignition wire connection that seemed to have solved the problem. I didn’t test ride the bike, though and a few weeks later the owner complained that the bike would be hard to start, run awhile and then the battery would seem to discharge again.
The bike was brought to me this time and I dissected the charging system once again, but found little to fault. I quick test ride left me stranded about 6 blocks from home, though. I walked the bike back to the house and checked for fuel to the carbs, as the battery got run down from trying to restart it after it died down the street. It turned out that the owner had drained the old gas/rust/water out and put 1 gallon of gas back in the tank, without telling me. When the petcock was removed the reserve function was plugged up so it wasn’t supplying gasoline to the carburetors. Arrrgh!
The petcock was cleaned, tank rinsed out again and 3 gallons added to the tank. Once the battery was re-charged the bike fired up sluggishly, but did run okay once it was warmed up for a few minutes. Using carb spray, some air leaks at the manifold/cylinder head junction were discovered. The manifolds didn’t appear to have failed, but it was decided to change both the o-rings and manifolds as long as it was all apart. The battery was again charged up to where it was holding about 12.5 volts at rest.
Changing out the manifold o-rings and manifold connectors was not a particularly fun task with the carbs and airbox in place, but using some brute force was eventually accomplished. Using full choke, a cold engine start was initiated and the bike barked to life much more quickly than before. The lack of air leaks and subsequent resetting of the idle mixture screws brought the 29k mile engine to life at all engine speeds. When the battery started out at 12.75v in the beginning, it remained at that voltage level after a 15 minute test ride. These bikes have instant ON headlights, so the battery drain starts as soon as the switch is turned ON.
Speaking of ignition switches… the ignition switch base cover was not securing the switch base contacts to the rest of the switch assembly. Pulling the headlight loose from the fork ears gave access to the switch mounting bolts and the whole assembly was unplugged from the harness. The aged harness connector was getting brittle, but still had enough strength to hold the switch contact connector securely. It appeared that someone had tried to replace the switch base cover previously, but the slots where the cover snaps into the switch base were still plugged up with remnants of the original cover tabs. Clearing the tab holes allowed a new cover to engage the switch housing base correctly and securely.
When Honda started putting the ignition switches up in the middle of the instrument cluster, problems have arisen in the older, hi-miles machines where the constant push-pull of the harness wiring as the handlebars are turned back and forth causes the switch base and cover to work loose. When the connector separates just a little bit from the switch base, power is interrupted or lost altogether.
The combination of a loose ignition switch base, lack of fuel, weakened battery from excessive cranking caused a whole cascade of problems that the owner was experiencing. After chasing out the gremlins and getting the bike running properly, attention was made to the rest of the bike which had run out of rear brake adjustment threads due to worn shoes. Replacements were ordered and installed, so now the bike’s owner has a better chance of riding a bike that operates correctly and is safe to ride for the summer.
Two more dead ones…
A good friend from Los Angeles brought down a long-dead 1967 Honda 305 Scrambler and a 1982 Honda Z50R Mini-Trail bike for revival. John had owned the bike for more than 25 years, buying it for its overall originality (some restoration work was done) and had never really ridden it. The Mini-Trail 50 was destined for his grandkids once it was brought back to life again.
The 305s are my specialty, so generally no surprises there, but not many Z50Rs have come my way in the past 30 years. Basically, they are about as elemental as you can imagine, but this one had me scratching my head for more than a few hours as repairs were made and tested.
Most of the little 50-70cc Honda singles have a simple magneto-ignition, a compact OHV cylinder head and tiny single carburetor, running an automatic clutch to make the package operate under the normally grueling conditions that are the life for Mini-Trail motorcycles. I was given a tune-up kit with the Z50R, consisting of a new spark plug, ignition points and a condenser. Removing the flywheel was the first order of business and that uncovered a magneto that had either been run uncovered in the dirt or just stored in a very dusty and moist environment for many years.
The inside of the flywheel, where magnets are located was coated with dust/rust which made the transfer of electrical energy impossible. The magneto base was similarly coated with dirt on every surface. The condenser wires are soldered onto the top of the unit, so you have to unsolder the old one first. Transferring the wire connections can be tricky if you have a cold solder joint or the wire ends are not tinned properly. The tune-up kit was an aftermarket brand whose parts fit the engine, but were really not all of the quality of OEM components.
Once the magneto base was cleaned and all components installed the flywheel was fitted for testing. Unfortunately, there were no signs of spark initially, so the flywheel was again removed. A closer look showed that the primary ignition coil base has rusted ends, which again work as an insulator against the effects of the flywheel magnets. Once a careful cleaning of the coil posts was completed the ignition finally showed signs of life giving off a nice little blue arc across the spark plug gap.
The carburetor was removed and found to be remarkably clean, however the pressed-in pilot jet appeared to be blocking fuel flow due to residue inside the .014” hole. The jet was twisted, pulled and finally removed for inspection and cleaning. Tiny tapered reamers were used to clear the passage, but when the jet was pressed back into the carb body, the fuel flow remained blocked.
With the jet removed once again, it appeared that the feed hole in the carburetor throat was drilled slightly off center, so that the blunt end of the jet was blocking fuel delivery. The end of the jet was beveled a little, but flow problem persisted to the point where the engine would run, but idle mixture flow was uneven, causing the spark plug to fuel foul leaving black soot on the electrode end. The engine would either not idle or would suddenly speed up to a fast idle. Mixture screw adjustments had little effect on the condition and finally a new carburetor purchase was made to eliminate what seemed to be the running problem.
The fuel tank was initially viewed as “amazingly clean” at first glance down the filler hole. When the tank was removed and the petcock unscrewed from the fitting, a little rain of rust particles poured out of the outlet. It appeared that some water/moisture had settled down at the bottom of the fuel tank, causing rust flaking to occur. It never was enough to work its way up towards the opening so at first glance, it appeared to be a clean tank. Rust bits were knocked loose and a new petcock installed with a screen to prevent rust from coming through the fuel lines and carburetor float valve.
These little engines often suffer from little or no maintenance, so the typical reason for them to be discarded is that no one has ever adjusted the valve clearances. The clearance is only .002” so over time the valves sink slowly into the seats and the result is compression loss, with hard starting and poor performance issues. Adjusting the valves often brings them back to life without a lot of extra work involved.
This bike was showing a bit of oil smoke in the exhaust, so the cylinder head was removed (requires front tire removal!) and the valve stem seals replaced and valves cleaned of old carbon deposits. In the end, the compression readings were over 150 psi, which is great for these small engines. With a new carb, correct ignition timing and fully functioning cylinder head, the bike now starts and runs well.
After an initial visual inspection, a big parts list was initiated including new air filters/tubes, spark plugs, carb repair parts, new cables, replacement hardware for the missing brake light switch and centerstand hardware to replace the undersized stand pivot bolts and a very long coiled spring that wrapped around the swing arm. The correct centerstand hardware consists of two special pivot bolts, a spring hook and short coil spring. The brake light switch stopper mount had been repaired using a small flat washer, tack welded into place. The switch bracket is welded onto the frame and this one was bent up at about 10 degrees from normal. While changing the rear brake cable, the brake arm was slow to move indicating that the brake cam lubrication was gone and corrosion was taking its place.
So, the rear wheel was removed to service the brake cam problem, only to find that one of the brake return springs had a broken end, so was just hanging inside the hub ready to fall into the drum at any time. New springs were ordered and the brake cam removed, cleaned and lubricated for normal function. The front wheel will need the same service as the brake cable pulling the brake arm is mostly non-responsive. The brake cams were sticking and the brake linkage had been installed backwards. These are the kinds of things that you must expect on a 50 year-old bike that has been stored for more than half of its life.
With overhauled carbs, petcock and new air filter assemblies, the bike was nearly ready to start back up. Fortunately, this gas tank WAS REALLY CLEAN inside, which is nearly unheard of given its age and storage situation. Compression checks were a bit under specs at about 120-130 psi, but that is enough to make them start and run. Often there is a thin layer of carbon or rust on the valve heads and seats which prevent a positive valve seal in initial running. Once the bike began to run, the engine sounds improved in the quality of exhaust tone and I suspect that valve sealing will improve with time and miles.
The ignition timing was somewhat close enough to run, but dynamic testing showed an over-advance condition on the left cylinder. The bike idled low enough to establish running idle timing before the spark advancer kicks in and kicks the spark timing up to the 45 degree (II) mark. With some 12k miles on perhaps the original engine, the internals are bound to be worn to some degree. The central camsprocket carries the spark advancer plate, weights and return springs, which are subject to wear and loosening of the rivets that hold the whole assembly together at those mileage markers.
The spark timing was established correctly, but the engine tends to want to rev up and then return rather slowly. Often, this is due to the carb slides sticking or throttle cable routing problems. New o-rings were installed on the carburetor flanges and insulators, so the manifold air leaks should not be an issue which could contribute to uneven throttle response. For reasons unknown, the main jets installed on the carbs were #120 vs. normal #130 mains. With today’s alcohol-based fuels, even larger jets might be required.
The handlebar upper clamp was cracked in the center, which was a first for me to encounter. A new OEM part was ordered from eBay sellers and was to be installed when a rather shocking discovery was revealed beneath the cracked part. What appeared to be OEM Honda CL77 Scrambler handlebars are probably those made for a CL350-450 model, which have a wraparound reinforcement in the center section. The handlebar clamp has no provisions for this raised section, so it was no wonder that the part cracked when the bolts were tightened down.
Instead of replacing the bars, the ends of the existing clamp were cut off and made into individual pieces which secure the handlebars and clear the raised center section of the installed unit. This is a bike that is FULL of surprises. While much of it appears to be original, it has obviously re-plated wheel rims and a few other chrome pieces.
This bike is one of the later 1967 models, which feature chromed front and rear fenders, plus the oval-shaped tail light assembly. A replacement lens was purchased to repair a broken stock lens on the bike. Other repair issues include a stripped out frame bolt hole which is used to secure the exhaust system to the chassis via the long, special 10mm head mounting bolt. Honda Scramblers are well-known to vibrate and loosen various parts along the entire motorcycle, so this was not a big surprise, but the repair of a shallow blind threaded hole is challenging.
There are well over one-thousand parts on a vintage Honda twin and each one has a purpose and function. This is another one of those “surprise” bikes which had been partially repaired/restored by someone who was certainly creative, but not one who went by the book on ordering and replacing damaged parts with OEM equipment. These are the challenges that many mechanics and owners face as they try to revive 50+ year old vintage Hondas. One must be patient and diligent in looking at all the parts and pieces during the rejuvenation process.
Bill Silver aka MrHonda