hey all,

my yz250 seems to be self propelling when at closed throttle, I'm thinking it could be jetting related although its strange, when I put the bike back together after machining the head for squish and cc'ing to bring the compression back down it ran fine and didnt do this, but now after maybe 2 hours use its now doing this, Ive had this happen before when I had a higher compression head,

could this be jetting if so where would I begin to start to rectify the problem?

the bike is a 2009 yz250, Pro circuit R304, V force V3, head squish 1.22mm, and ran on 98 octane fuel.

any help would be much appreciated.

I havent seen to much of this come through the shop. When saying it self propels are we saying that the bike will rev up? If it is I would suggest perfofming a compression test and determine what we are at. Also try dropping down to 87 octance and determine if the problem is still happening. What are we running for a plug, oil mixture?

it will just kind of go "gung" and jerk forward slightly,

the oil mixture is 40:1 and the plug is a 9 I've tried both iridium and normal and both seems the same, I'm going to try an 8 tomorrow.

how many psi would standard comp be?