ok im working on buddies 400ex. he had rebuilt and after he got it back its been hard to start and misses prety bad. but when warmed up its alot better. it kinda hits and misses.. electrical???? spark plug????? what you all think it could be.. i get it to fire and misses and dies know i cant get to start and run it will fire once and awile..


and another thing it has like header type thing on it and there both pipe got cracks one side gets really wet gasy... and other side is dry... could have it dropped a valve....cuz it wont start and run

 

400EX are difficult to start when its cold

 

oh and you can change your spark plug also its always better