Since I bought this yfz it has had a problem with missing at the high rpm range when I really get on it. No problems idling or at any other time. I've cleaned the carb and I don't think it's a fuel problem.

The guy I bought it from said he put a new stator in it. I'm thinking either he was chasing the problem or it is the problem. Someone recommended replacing the rev box saying that it may be bad.

What do you guys think?

 

main jet to small

 

Changed it. Actually bigger than recommended by dynojet.

 

check the timing.. if he replaced it.. it may be off a degree or something

 

Check your plug gap.

 

does it have the stock pipe on it.. my buddy had the same problem and it had no power with his when it was new and we took the tip off and it ran fine after that. if not what pipe do you have and what jets are in it.

 

then maybe to rich..

 

Not stock (check sig), not rich (checked jetting), gap good. Thanks for the suggestions though guys, much appreciated.

Good suggestion speedy on the timing. To make sure I know what I'm talking about I need get to top dead make sure cam chain marks line up then make sure the T on the other side of the case if visible thru the hole? Thats how I did it on the 400ex anyway.