Friends of friends drop my name to their friends, from time to time, when no regular motorcycle shops will touch their vintage Honda motorcycles. Recently, the driveway was loaded up with a W650, a 1971 CB500Four (see earlier story), a CL360 Scrambler (only 2 years of production) and a 1974 XL350 Dual Sport model.
The CL360 was suffering from a mid-range to high speed misfire, leaking fork seals and a knocking sound inside the engine (!). The XL350 was suffering from hard starting, blowing fuses and needing a general tune-up. The owner, who is a good-sized man in his 40s, started the XL350 for me but stated that sometimes it would light up on the 3rd kick and sometimes it took 15 attempts to get it to fire and run.
The bikes arrived in two waves, with the CL360 coming in first. While the owner remained to watch the initial testing and evaluation of the noises and misfiring, a compression test was run, ignition timing was checked (somewhat challenging because the stator had been replaced and the index mark was not present). The engine noise was cyclical and the source seemed to be the known recalled cam chain tensioner parts, judging from the sound. There was a factory recall on the tensioner blades from AHMC, shortly after the whole 360cc range of models was produced. Hopefully, most of the bikes being sold and used during that time would have been subjected to the replacement parts, however one can never rule out the possibility that more than a few machines were missed during the past forty years.
1975 Honda Cb360 Engine and Engine Cooling, engine Recall | Apr 24, 1975 is the title of the recall notice.
Honda’s supply of recall parts has been drained over the past forty years and the bean-counters apparently thought that there was little need to continue production of the required parts. Apparently a private company has stepped in to manufacture the needed parts to OEM specifications: http://www.common-motor.com/honda-360-cam-chain-tensioner
After setting valve clearances to specifications of .002” and .003” (intake and exhaust), the camchain tension was checked by rocking the crankshaft rotor back and forth by the central bolt. Watching the end of the camshaft (points cover removed) gives an indication of whether there is excess slack in the chain due to a broken tensioner. In this case, the cam was following the crankshaft directly with no appreciable slack, which was not the expectation one would associate with a broken tensioner. Loosening the adjuster bolt and tapping on the end of the tensioner adjustment rod had no effect on the camchain tension and ultimately the engine’s clicking sounds which persisted. Having the owner present actually was helpful for both of us to verify that all the possibilities were checked and that the source of the noise remained a mystery.
Leaving the knocking noises for awhile, the next step was to remove the carburetors and clean all passages and jets, plus looking for worn, damaged slide diaphragms and cracked intake manifolds. In general things looked pretty good, but the diaphragms were old and somewhat stiff in their response movement. Still, there were no holes or tears, so the carb rack was reinstalled. Subsequent test rides proved that the mis-fire was still present, which left electrical sources to explore. Both of the ignition coils were measuring out about 4.5 ohms, which is normal, but the spark plug caps, which actually looked like non-resistor types measured out about 8-10k ohms, instead of 5k ohms. Replacement of the spark plug caps cured much of the misfiring but it felt like there was perhaps some mid-range leanness where the primary and secondary main jet circuits overlapped. The carb jets were all stock and standard sized, but a bump up on the primary main jets might cure the rest of it. It has been often demonstrated in recent years, that that today’s alcohol-infused gasoline cause engines to run leaner than before due to changes in fluid viscosity and reduced energy content. In many cases, an increase in the main jet size, usually just one step, will cure that lean surge condition.
The fork seals were leaking badly, so that was the next task to complete. These fork designs were pirated for use on the CB400F Super Sport in 1975, so the disassembly procedure was known. What hindered the easy replacement was that the 8mm bolt which holds the inner damping rod down in the fork case was seized up in the fork housing and even use of air tools just stripped the Allen head hex out of the bolt head. Now that’s a problem! The “Plan B” step was to drill into the bolt head and drill it off of the rest of the bolt shaft, releasing the damper rod and allowing the fork to be disassembled. After some drilling was done, a screw extractor tool eventually allowed the bolt to be loosened and withdrawn. Once the fork seal was replaced, the remains of the bolt were too weak to hold the torque of the tightening process and the head sheared off completely.
Digging through some random bolts, a thin head bolt from a brake backing plate was slotted and reduced down to allow entry into the fork housing bolt recess. The screw slot was done with a hacksaw, so didn’t allow for a lot of tightening torque using a thin blade screwdriver. It was good enough to allow the fork to be reassembled and reinstalled, but a day later there was some fork fluid seeping around the bottom of the fork case, so a new bolt and washers was ordered from Honda to affect an appropriate repair next week.
With the CL360 set aside, the focus was on the XL350, whose carburetor was removed for checking and cleaning before following up with a valve adjust, camchain tension adjust, point gap and timing adjustment and hopeful easier starting. Unfortunately, that’s not what happened, much to my dismay. T would have been preferable not to have had the XL350 come over, due to the fact that the bike is kick-start only and Bill’s 8th month-old right knee replacement limits range of motion and strength during attempts to start the engine. After just a couple of vain attempts, the spark plug was removed to check for spark and there was none to be observed. So, how that that happen? The owner brought in a running bike and now it doesn’t have any spark to start the engine after just basic maintenance work.
Isolating the ignition on the XL350 is somewhat easy, as it has a magneto style spark system, which allows the street-legal lights to be removed, along with the battery for off-road use. Instead of the all-in-one type of flywheel magneto, the components are spread around the chassis; the primary coil is part of the stator coil set inside the flywheel, while the coil and condenser mount up on the frame beneath the fuel tank. The contact points are located off the end of the camshaft and incorporate a mechanical spark advance unit. The early bikes were setup to fire at 15 degrees before TDC, but a service bulletin indicates that there was a modification to fire them at 5 degrees before TDC instead to make starting easier. The points were set up to open at the prescribed marks, but nothing was happening at the spark plug. The plug cap was checked and it was found to be over the specified 5k ohms. The condenser is attached to the ignition coil, so both must be replaced as a unit.
Use of a 12v test light plugged into the primary pulse coil indicated some energy being generated at the stator, but it is very difficult to measure with a volt/ohm meter while you are kick-starting the motor over to generate the signal. The owner had returned to pick up the CL360 and observed my testing results. It appeared that the coil might be shorting out internally, coupled with the high resistance of the spark plug cap, so a new coil and cap were ordered from the local Honda shop. The $90 coil came in within two days of the order, but installing it on the bike did not improve the spark output whatsoever. So, what’s left now? A clumsy attempt to measure the primary coil output showed less than 2 ohms on the meter and only micro-volts being sent up the wiring to the coil. Removing the dyno cover to check for damage or defects proved fruitless, but the last thing on the list was the stator assembly. Honda seems to have used the same components on both the earlier XL250 and later model XL350s. Finding a nice looking unit on eBay, which came from a 1977 model, seemed like a safe bet, so it was ordered and received within two days, coming all the way in from Idaho! These parts are NLA from Honda now, so good used ones are the only option at this point. Incidentally, the replacement coil had an ohm reading of more than 5 ohms. The meter was having problems stabilizing, so it was somewhere between 5 and 10 ohms, a good bit different that was seen on the original failed part.
Happily, once the stator and new gasket/seal for the cover were all buttoned up, the long-lost spark at the plug resumed its appearance. With everything secured, the bike was kick-started successfully on the third try, even with the weakened kicking knee of Bill. This was what had been hoped for from the beginning. The slowly failing primary coil had thrown the troubleshooting efforts off-track during the process.
It would have been helpful had the factory service information been available, but neither searching on-line nor digging through limited repair books on hand gave sufficient clues as to what would have been proper specifications for the stator and the ignition coil sets. Thankfully, the owner was very understanding and quite pleased in the end that both bikes were up and running as good as they could be under the circumstances. For Bill, there was a lot of learning to do on the magneto ignition setups for the XL250-350 models.
The CL360 will be back for repair of the leaking fork bolt problem, but more importantly one of us will have to tear into the top end of that motor, to see just what is going on inside that is causing the knocking noises before they get substantially worse.
With both of those bikes off the driveway, it was only natural that an emergency call came in from my friend Marc, whose CB350F had suddenly puked a substantial amount of oil on the driveway, just after he had made a 15 mile freeway trip back home from work in downtown San Diego. His video clip was scary enough to make us both think that something catastrophic had occurred. Fortunately, he lives within a 15 minute drive, so some inspection tools were brought out to his house to have a quick look at the damage and cause of the leak. The actual cause was the shift shaft seal pushing itself clear out of the engine cases. What was probably the original factory seal had softened with age, heat and oil exposure to the point where it became very mushy and unable to withstand the crankcase pressure pushing from inside the engine at high speed. Had it happened to him on the freeway, his off-ramp departure might have proved to be disastrous with an oiled-up rear wheel that he never would have known about until it was way too late. Anyway, his motorcycle angels were hovering over him and lead him to safety before the big final oil dump took place.
Generally, the shift shaft seals give some warning as they wear and begin to weep oil past the seal lip edges. Little trickles of oil will drool out of the counter shaft cover drain holes, in most cases. Quite a number of shaft seals have needed to be replaced on bikes that have come through Casa de Honda in the past few years. If you are beginning to see some drips coming down from the shift shaft area of your bike, do not wait until it is too late to change them, please! Do it NOW!