Forum bmwbike.com

I am trying to get info for a friend.We are in the Bahamas.Bike has compression,new carb, good spark,wont start.Timing appears to be correct visually but it misfires as if the timing is incorrect.Would really appreciate some help, info or a person to talk to.

What kind of BMW? By "new carb", you appear to have a single cylinder R25 or R25/2, for which 1951 was a transition year.

When you say "timing appears to be correct visually", how are you checking the timing? If the bike won't start, how can it misfire? What do you mean by misfire? I am not sure that timing causes misfire.

Perhaps the bike is backfiring after repeated attempts to kickstart. This would be caused by vapors in the exhaust system after flooding. Timing could be a factor. The carb also might not be properly adjusted.

I would check valve adjustment, check that points are just opening on the S mark, check that the carb is clean, the jets are clear, and the idle air screw is set initially 2 turns out.

Then there is a starting drill to master. For a cold bike, I open petcock, depress tickler for a second, press in ignition key, open throttle a tiny amount, and kick hard twice without stopping in between. If you mess up the starting drill and flood the engine, even a well-tuned engine will then be hard to start.