hello, new to the forum here, but anyways im gonna cut right to the problem, i have a 1992 polaris trailboss 250 with the old school 2 stroke in it, one day on a cold morning i was riding home, and i just stalled out, but it started right back up but sputtered, ran like crap, and flames were shooting out the exhaust manifold on the front of the engine, then i stalled again, this time no luck, had to get towed back home, the rings im 100% sure are fine. it never smoked or anything before. The motor ran strong, the motor has compression, and amazing spark, and it wont even fire on ether. so what gives?

 

What is the compression reading? If it wont fire up on ether,it's usually a compression problem or crank seals leaking that can keep it from running.

 

havent gotten around to check the exact psi but it should be plenty. i heard crank case seals are a common problem on these, just making sure there arent any small things i might not know about this particular machine, before i replace the motor since i have a spare one on hand.

 

Possibly a blown head gasket if not the things OPT said? Was it making any abnormal sounds while it was running?

 

it needs a good 100psi of compression to run. if it's backfiring as mentioned it also sounds like it might be running lean.