Won't run right when hot, keeps cutting out, need some advice

[lilredhonda79]

Alright I'm running outta ideas, I'm gonna try and rejet it sometime, it'll run fine till it gets warmed up, then when you hit the throttle real quick it will cut out, it runs like this at low idle as well but driving with higher rpms it runs fine, the plug seems to be burning fine, but if I put a new plug in, it will run fine for 30 miles or so then it will start cutting out and spitting and sputtering, I put a 11:1 piston in with a stage two hot cam along with already having an hmf slip on, I put the k and n air filter last fall and now this spring it doesn't wanna run right, a small gas engine shop up the road said check valve clearance so I did, it ran right for a little more then starts doing the same thing, but I'm wondering if something broke loose somewhere because it first started doing it when I raced it this past spring, so I'm basically looking for suggestions on how to fix this problem, like I said I think it might be jetting so jetting suggestions would be helpful, I have the air box and lid still on, 11:1 piston, stage two hot cam, and k and n airfilter, and I haven't tinkered too much with jetting since I've had it I put my buddies extra 160 in it and it did the same thing so if I can't get it it right with jetting ill tear it apart and see how the valves and top end look, any help would be appreciated, thanks!!

[CJM]

Too lean, its overheating. I ran a 175 main and 42 pilot with a similar setup.

[LxMxL97]

Too lean, its overheating. I ran a 175 main and 42 pilot with a similar setup.

I also think that's the problem I had a 180 in mine

[lilredhonda79]

Alright thanks, appreciate it, I'll give it a shot

[DragonGunner]

Could also be a sticking choke. Also had this happen on a ATC, vent hose out of gas tank was blocked, would open up the cap and put back on and would run good again for awhile then start acting up again. Hose was blocked. Hopefully the bigger jets will solve it....but if not.

[JOHNDOE83]

try 190 main jet or even higher, its not to rich until it wont go full throttle. If that happens back down 5 jet sizes and youll be good.

[JOHNDOE83]

read this

http://www.jetsrus.com/FAQs/FAQ_rejetting_101_how_to_rejet.htm

[JOHNDOE83]

http://www.jetsrus.com/FAQs/FAQ_rejetting_101_how_to_rejet.htm

[lilredhonda79]

Thanks, that article was pretty helpful, it definately sounds like jetting

[MtnEX]

I would also go ahead and check compression on it too.

Is it really a bit stubborn to start up and get to stay running when cold?

A K&N filter is a pretty good way to get everything filthy and also trash a motor at a race. The XC races I run are brutal dusty if it's dry and that fine airborne dust sucks right through a K&N filter.