Sunday, October 9, 2016

Two out of three; vintage Honda bikes are runners now…

The S/CL90 project bike had gotten to a running state now, but not without more headaches along the way. Unable to find a decent point plate set quickly, a careful disassembly and cleaning of the old point plate eventually yielded a functioning unit.  The slide throttle parts didn’t seem to agree with the a/m café handlebars being used, so the old Wassel-type twist throttle was cleaned up and reused with a shortened throttle cable.
When the first attempts to kickstart the bike were made, the clutch slipped endlessly. Off with the clutch cover, checked the clutch assembly and found nothing wrong, however when the locking washer was installed below the clutch retaining nut, the outer edges of the washer pushed up against the inner edges of the clutch hub and released it every time the nut was tightened down. The immediate cure was to leave the locking washer off and tighten the nut real snugly. Once that was remedied, the engine would kick-over but still not start.
Checking the points with a test light revealed that the point wire was somehow grounding out all the time, so that was repositioned and spark returned to the plug. The next attempt at starting the engine met with limited success as soon as the engine lit off, oil started pouring out of the clutch cover gasket. The early engines have specific gaskets which I had ordered specifically for this installation, however the oil flow slot was a little too large and there was a gap at one corner allowing the oil to come bleeding out relentlessly. At least I knew that the oil pump was working well!
Some RTV in the gasket slot, left for a few hours seemed to mend the problem and the bike restarted, warmed up with no further leaks and then suddenly shut down completely. Repeated kicking did nothing for it and the plug was rechecked for spark which it had and there was fuel in the carb bowl…. So what now!!??
Checking the compression, I discovered that the readings had dropped from around 140 psi to 60psi all of a sudden. That is a good reason for the bike to quit and not restart again… So, off with its head! Somehow a tiny fragment of aluminum had gotten sucked into the intake and lit right on the edge of the intake valve seat, propping it open which caused the compression loss. Removing the tiny piece of material, reseating the valve and reinstalling the head made it all back to normal once again. Bike starts and runs well, shifts gears, stops and just needs a proper exhaust system.
The big problem for this S90/CL90 marriage is that the early S90 engines have a twisted intake manifold and a diagonal bolt pattern in the head for the manifold mounting. Additionally, the exhaust port is on a 45 degree angle vs. the later 90 degree angle for CL90 exhausts and later S90 applications. The S90 came with a short upswept aftermarket pipe and tiny rusted muffler. In order for the CL90 muffler to work on this application either the head has to be changed to the later style unit or the exhaust pipe needs to be cut and re-welded again to achieve the correct exhaust port angle. For the moment, it sits as it is while work continued on both the C72 engine overhaul and the “free” XL200 Enduro Honda which had received a new piston/rebore recently.
The XL200 engine installation went badly, at first; due to misuse of the two top engine mount bolt spacers. Swapping the spacers, which have different lengths, made the engine bolt holes all mis-aligned and it took stepping away from the bike overnight to reconsider the problem, which was pretty obvious once all the facts were considered. Swapping the spacers made the engine bolt installation easy and parts continued to be reinstalled as the afternoon progressed. Once the electrics were all connected, the engine was kicked over to check for spark… and none was noted. These engines have a CDI ignition and the spark can be hard to see in broad daylight. Even so, nothing seemed to be happening so time was taken to consult various forums and U-Tube videos trying to come up with some troubleshooting steps that were appropriate. There was voltage coming up from the stator to the CDI and readings on the coil and pulse generator seemed to be okay. CDI modules were somewhat suspect back in the early days of the technology so perhaps mine was fried. A quick check on eBay found a whole wiring harness with a CDI box attached for $40 delivered, so I took a chance that this might solve the problem. The parts came in just 2 days, but swapping in the CDI box didn’t seem to have a positive effect.
In my research, I discovered that the KILL switch is actually a continuity switch and not one used to ground out the system. The switch knob was stuck in ON position due to years of sitting outside. I was able to remove it, disassemble the contact parts, clean everything and reassemble it successfully. Once the switch was reinstalled into the system, I checked for spark once again. It is difficult to do on these bikes, as they are kickstart only and holding the plug against the head while kicking it over is a difficult chore. I wasn’t sure if there was spark or not, so I put my finger down between the plug and the head and kicked it over again…. ZING! Bingo, we HAVE SPARK now!  The KILL switch was probably all that was wrong in the first place, but that’s how we learn these things, isn’t it?
With the fuel system ready to run, spark at the plug and good compression, it should have started right up, but there seemed to be some problems getting fuel to the plug, so a little gas priming was done from the fuel bowl after the idle jet was rechecked for being clean and clear. In checking, I did discover that the two carburetor nuts were finger-tight so those were snugged up! SOMETHING worked; as the bike finally came to life after numerous more stout kicks and it settled down to a nice idle fairly quickly.  
With a live engine being fully realized, I cut a new drive chain for the bike and adjusted it up with the snail-type adjusters on the rear axle.  Once that was installed, the bike was ready for the “trip around the block” run to see if the clutch was stuck or other maladies would become apparent.  Surprisingly, the transmission dropped into 1st gear and off I went, progressing up through each gear cleanly and smoothly. Even the speedometer was working! The only problem was that at the end of the test drive the bike wouldn’t shut OFF! Turning the ignition switch to OFF and the KILL switch to OFF did nothing to shut the engine down. I quickly removed the headlight bulb assembly and found the KILL switch wiring harness. Plugging the loose GREEN wire into a nearby GREEN wiring double connector finally killed the engine. Problem solved… or not! When I tried to restart the engine, it wouldn’t fire again until I unplugged the green wire. When I tried plugging the green wire into an adjacent double green wire connector, the engine would KILL if the KILL switch was turned to OFF, but only the KILL switch would kill the engine. The ignition switch didn’t affect it whatsoever. I think I better stay with the older bikes, where I can see and measure what is going in and out of the electrical system more easily.

The last bike on the list is the C110 Honda Sports Cub, which has a simple magneto ignition system, low compression pushrod engine and weighs next to nothing compared to the other two machines.


  1. The handlebars are pretty similar to those of the mountain bike, extending usually to shoulder width, which allows the rider to sit up right very comfortably. best hybrid bikes under 200