August 28, 200916 yr Hi Guys I bought a model 91 on E-bay about a month ago and cannot start it. The engine was reported to be a runner - but that's another story! When kicking over I get a god spark - the plug's a BP5ES, but the engine doesn't fire. I've had the carb apart (Amal Concentric) and notice the slide (with needle) is a very tight fit in the bore of the carb housing. I think this could be the cause of the problem and intend to polish up the slide using crocus paper or similar to make it freer to move. Any other places to look? Roger B
August 28, 200916 yr Is the timing right? Check that the flywheel key has not sheared, or as in the Bult I bought, if it has a key at all!
August 28, 200916 yr I'd take the carb apart and make sure it's clean. ESPECIALLY the pilot jet. And that the slide moves freely. Then check for spark.
August 29, 200916 yr Only takes three things for the bike to run. Spark, fuel and compression. I agree the timing should be checked. You have cleaned the carb, thats good. Did you make sure the pilot jet was clean? was the pilot passage in the carb clear?. Will fuel overflow the float bowl when the tickler is pressed. When installing the carb I always make sure to use a slight bit of Loctite 515 on the mating surface to make sure that no air leaks will occur. Also Bultaco's are well known for needing crank seals. They are easy to replace and are also easily available. Make sure the cylinder base gasket isn't leaking. I've seen this many times on Bultacos. It can only be 3 things or a combination of three things Steve
August 29, 200916 yr Author Many thanks to all for your various replies. I'll look into all of them when I get back from holiday in a couple of weeks' time and let you know outcome. Regards Roger B
October 11, 200916 yr Author Hi All Since my last post I re-assembled the carb after checking all jets and passages were clear. Also float and needle valve looked OK. I managed to fire the bike a couple of times then the engine died on me. Found the HT coil lead to spark plug was broken so bought a full electronic ignition from Bultaco UK rather than mess around changing points and condenser etc. Just fitted that and am getting a good spark but still engine won't fire. I'm getting fuel seeping out around the tickler on the carb but the plug is dry?? Any suggestions? Should I now check crankshaft seals and compression of concentrate on the carb? Roger B
October 14, 200916 yr Hi AllSince my last post I re-assembled the carb after checking all jets and passages were clear. Also float and needle valve looked OK. I managed to fire the bike a couple of times then the engine died on me. Found the HT coil lead to spark plug was broken so bought a full electronic ignition from Bultaco UK rather than mess around changing points and condenser etc. Just fitted that and am getting a good spark but still engine won't fire. I'm getting fuel seeping out around the tickler on the carb but the plug is dry?? Any suggestions? Should I now check crankshaft seals and compression of concentrate on the carb? Roger B If you don't know the age of the seals, replace them. You'll be chasing carb and electrical demons possible all for naught. Does the electronic ignition need different timing?
October 26, 200916 yr Author Hi Swoosh Dave Many thanks for your suggestions. Did a compression test and managed 110psi when kicked over. Is that OK? Took the carb apart again and found the main jet completely blocked and could not clear it. Other jets and passages found clear. The slide appears worn and when referring to Amal carb website they recommend renewing it - so I've just ordered a new 627 Amal concentric Mk.1 from Amal UK. Would prefer to change the carb rather than crankshaft seals at this moment. Will update you when the carb's fitted in a couple of weeks. Regards RogerB
October 26, 200916 yr Are the crank seals able to be replaced without splitting the cases on these bikes?
October 27, 200916 yr Are the crank seals able to be replaced without splitting the cases on these bikes? Yes. Gotta take a bit of stuff off, but cases stay together.
October 27, 200916 yr Gday, just a quick thought regarding the carb, Are the ones on those Bulty's a bolt on flange type? If so, don't over tighten the nuts, its a classic way of making the slide stick. If they use a rubber, just ignore me... Cheers, Stork
October 28, 200916 yr Author Hi Stork955 Thanks for your interest. My carb bolts to the inlet manifold using a 2-bolt flange with a rubber pad between the carb and the manifold. I don't think I overtightened the flange bolts so maybe no effect on the slide. The carb looks original and the slide is worn - so it's done a few miles no doubt! Regards RogerB
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