i just finished rebuilding my topend with a wiseco piston, bored std .50 over and new gaskets. Well to make a long story short i got it all together except for the whole exhaust system, got excited and started it up without the exhaust on, then it happend, it blew this little (maybe 3 inch blue flame) out of the head, i quickly turned off the quad. Is this normal? do i need to maybe re-jet? or do they all do that without the exhaust on? i am at a lost because everything sounds good, no piston hitting the valves or anything of that sort. this was my first 4 stroke top end rebuild, i have done mostly 2 strokes so any help would be nice. thanks.

 

shouldnt start it without the exhaust off because it doesnt allow the valves to cool from the backpressure and u could ruin the engine

 

i had it on for maybe 25 seconds max. you don't think that did anything to the valves do you?

 

prob not

 

what about the flames though? any ideas? thanks.

 

probably just a backfire...put on the exhaust and try it again.

 

The fuel was still able to burn, and when it hits fresh air it still burns. If I rev at night I can see a small flame come out the back

 

yea thats normal most motors will do that. you should have done it at night it would have looked cooler