BSA WM 20 jerking with gunshots (Edited by Author)
Good morning everyone. I hope you can help me. Why was the bike jerking in short ride? It stalled and restarted in a fraction of a second. After a long ride (270km), it stalled completely. It restarted with the timing lever fully retarded. Then, immediately after putting it back in the correct position (fully advanced), it was fine, but with gunshots from the exhaust pipe, and after 100 meters, it stalled completely.
Hi Daniel,
If I understand you correctly it could be air getting into the exhaust pipe, is yours nice and tight in the barrel?
There may be other possibilities that others can suggest, good luck!
It sounds as if you might want to check your fuel. Were you near the bottom of your tankful? Could it be debris in the line? Around here (USA) the problem is often water that has precipitated out from ethanol fuel. This sinks to the bottom of the tank. When running it doesn't seem to be much of a problem, but after a stop it can be!
I think it is possible your magneto is failing. These symptoms suggest a failing capacitor. It is inside the magneto windings and in order to fix it the magneto will be have to be removed and completely overhauled. I have seen exactly this problem before.
REgards, Mark
I saw your post Daniel but I didn't feel qualified to diagnose the problem from your description. It could be any amount of things from nipping piston or sticking valve or any of the things already mentioned...or something simple like a blocked jet or drilling in the carb. Ron
