Motorcycle Repair: gas coming out exhaust, exhaust stroke, dirt bike

Question
hi chris, I,m trying to get a 1980 pw80k dirt bike going and when i tried firing it up gas came out exhaust where it bolts to the engine .i was wondering if you knew what the problem might be. is it a cracked engine or what?

Answer
Hi Tom.
 You have a couple of possibilities here besides the loose exhaust manifold.

1)  The bike is running rich and not able to burn off the fuel so it expells it on the exhaust stroke, or

2)  the ignition is weak and not able to burn off all of the fuel and expelling the excess on the exhaust stroke, or

3)  the valve timing is off and the fuel is not all being burned off before the exhaust valve is opened.  This will also cost you performance and power.

Check the ignition circuit for loose connections or intermittent shorts.  Check the valve and ignition timing as well.

Good luck.
FALCON