Normally I'm pretty good with engines, and I had this thing running perfect for a while but it has developed this mis/stutter at I what I would guess is around 5000 rpm under full throttle. Throttle response is good until this point and I don't have any issues with part throttle riding.

I have jetted up and down 1 step and not seen any improvement. I changed to a new spark plug with no difference as well. The powervalve is working correctly. I thought I had a blown head gasket so I replaced it, but it is still doing the same thing. The top-end is fresh as of the beginning of this season and it still has 180-190 cranking psi. Also I've repacked the silencer thinking this might be the cause.

So I'm a bit stumped. I was hoping someone might read this and have a suggestion. All I can think it might be is a bad stator or crank seal on the oil side, (the mag side was replaced when I did the top end).

It does have a small leak where the pipe slips on the header flange because I can see smoke shooting out when I first start it, but I can't believe that would be enough to cause this issue.

Any suggestions, from someone who has encountered similar problems?

 

had this happen on my bros blaster....a bolt from Gosh knows where got stuck in the reeds...made it run like that

 

In case anyone else ever has this problem it was my timing. I lined up the marks on the stator and its running stronger than ever.