Testing & Repairs

Riding the Sherpina at the 2007 CATRA Vintage Trial.

Following the Stage Two modifications I decided to test out the changes by riding a few trials events. That doesn't mean I didn't have to put any wrenches to the Bultaco, quite the opposite. Riding a 35 year-old competition motorcycle, no matter what discipline you're riding it in, is going to require routine maintenance and repairs.

One of the problems I had was with the kick start lever, which I mentioned back here. The problem stemmed from the fact that I had the older style kick start that had the swivel piece held on by an external snap ring. Over time the lever wears and the snap ring no longer sits in the groove. The later model kick start lever is tapped and uses a screw to hold the swivel piece onto the lever. Of course my first repair was to use a new snap ring, but when that failed as well I gave the kick start lever to my machinist friend Phil Steel (no relation) who drilled and tapped the end of the lever and installed a bolt. Problem solved!

Pushing my kids on the Sherpina at the 2007 SMOG East Trail Ride.

Another issue, that has been and ongoing problem, is the fuel tap. Years of built-up varnish plugged it up so bad that during one trial the bike kept running lean going up hills or on long transfer sections. My solution that day was to stop half-way up the hill and breath into the tank overflow hose while tickling the Amal carburetor. I would also do the same before each observed section, just to make sure I didn't run out of fuel and take a five. By the end of the trial I was pretty light-headed from all the fumes and my last loop was actually my worst loop. When I got home I drained the tank, pulled off the tap and cleaned it out. I'm fairly anal when it comes to draining the tank and carb float bowl after use. One I don't want the tank to go soft and leak from the ethanol-blend pump fuel. I also don't want the carb jets to foul up from, once again, the ethanol-blend pump fuel. Unfortunately the gasket in the fuel tap is slowly starting to disintegrate. Even though I'm sure this is normal for a motorcycle of this age, I'll go ahead and blame the damn ethanol-blend pump fuel for this too. I'll probably have to splurge for a new fuel tap or find the correct fitting and install an inline fuel tap (remember, I'm cheap... errr... thrifty). I've never been too concerned about having a reserve. I've always ran my enduro bikes on reserve because if I do run out of fuel, oh well. Then there's the people who say running on reserves lets all the crap in the bottom of the tank into the carburetor. That is true, but if you run on reserve all the time little, if any, crap settles in the bottom of the tank.

At one vintage trial a friend of mine, Bob, was riding a Model 92 Sherpa-T 350. The bike lost spark and quit running after the first loop. After sitting a while it restarted, but again ran for only a short period before losing spark. This is actually a common problem with Bultacos that use the Femsa breaker-point ignition. The capacitor is located behind the flywheel and, when it gets hot, shorts out internally causing the ignition to lose spark. The solution is simple, add a condensor up to the frame near the wiring junction block. Almost any automotive or small-engine condensor will work, but I went the cheap (Scottish) route and just moved the stock condensor. While I never had any problems, at least now I have peace-of-mind that the condensor won't fail.

Condensor relocated up to the frame next to the junction block.

Another item I wanted to address was the clutch pull. Now I realize the Sherpina will never have the light pull of a modern bike with a hydraulic clutch, but it took the strength of all four fingers to pull the lever back. Even though vintage trials is supposed to be no-stop, there comes a time when you need to pull in the clutch, rev the engine and fan the clutch to keep from stalling. Also, if you check out any photos of vintage trials, you always see the riders with one-finger on the clutch lever. Well my clutch was, at best, a two-finger pull. Several factors contributed to this. One being it had a short actuation lever. The lever was also angled on the splines requiring more effort to actuate. There was a return spring that would bind during travel of the actuation lever. Finally the cable was cut too short, by me, to re-angle the actuation lever on the splines. To correct this I scrounged a longer actuation lever off another Bultaco. It was actually the actuation lever off the front brake. The splines for the clutch, brakes and probably the shifter are the same size. Next I purchased a longer cable to allow me to re-angle the actuation lever. Finally I pitched the return spring. This lightened the pull dramatically allowing the clutch lever to be easily pulled by two fingers or even one.

Finally I added some Bultaco decals to the tank just like to replicate the look of the original Sherpa-T. While this addition did nothing to improve performance, it does make the Sherpina look quite spiffy from a distance. While it's definitely not museum-quality, it at least looks good particularly from a distance.

Left side of the Sherpina.

After all this work you have to wondering why I would want another bull.