SPITTING BACK

[JJ MARSHALL 0]

i've got a B/S cast iron engine model 300421 that i'm try to get started when turning the engine to try to start it will fire back through the carb.just did a valve job , has new key. was doing the same thing before i did the valves.i can install a air fitting into the spark plug hole and feed air and turn crank to top dead center and no air will come out of the carb or muffler can hear some escaping into oil pan.any ideas? THANKS JJ

[Leroy 0]

Air is a pretty small molecule. Worn rings and no oil on the cylinder walls would let the miniscule molecule of air blowby the rings.

[JJ MARSHALL 0]

I can understand some air getting by some the rings that have alot of ware. i can not understand why it fire's back through the carb? JJ

[Leroy 0]

The intake valve may not be not seated, maybe seat needs dressed, Spring worn. Other folks maybe to busy to respond to this. I din't see any suggestions, so i offer a couple.

[JJ MARSHALL 0]

THANKs LEROY but i think that the valves must be seated because when i turn the engine to top dead center with the air still hook up ther is no air escaping through the carb or muffler. at top dead center both valves should be close. JJ

[Kent 435]

Sounds like a timing problem of some kind to me... if you're sure it's not the flywheel key, could you have somehow changed the timing when you did the valve job?

[JJ MARSHALL 0]

well its running replaced the module that had been put on engine to replace points and it started up. could be that the module was letting it fire at wrong time? JJ