Engine Break In Problem


New member
Just assembled an engine and am in the break in process. During one of the runs, the motor coughed, spit and died. My first thought was timing (34*) or ignition, so I checked the flywheel key and coil gap (0.045). They both seem to be good. Rechecked the valve lash and its at 0.002 to 0.003. The spark plug is dark but not fouled. When I try to restart, it backfires through the pipe sometimes. Is it possible that some trash has got in the carb? Maybe something in the new fuel pump gotten into the carb? any other possibilities?

Thanks in advance
did you use a timing wheel an a timing wheel to set the timing? 9 time out of 10 its going to be the timing. when you take the rpms up does it sound lazy?
Yes set the timing with a degree wheel. It was running good for the first 4 break in runs. Just sputterd and died.
check the flywheel key again. did you take the flywheel off an look at it hope this helps

Yep, looked at it, took it off, was just where it was supposed to be. Put it back on, fired it up, idled about 2 minutes and sputtered to a stop.
simple stuff first. plug /fuel , Next is valve lash. carb and then rod bearing Got any test equipment ie. compression gauge.
pop in ehaust is indicative of timming or valve seal. upon assembly did you check rod clearance. the obvious you did put oil in , drain and inspect the oil.
GOT IT !!! Was the plug after all !! Lesson learned .... Even if it doesn't looked fouled... it could still be. Thank for all of the responses.