I just putt a new set of rings and had my head ported and polished in my raptor. Now it spits and sputters when i get it up around hafe and full rpms and it has trouble starting now. I have a 686 kit, ported and polished head, jets, LTE pipes, and a K&N pro flow kit. I am runing a 165/170 main jets. I dont know if thats what is wrong with it. Thanks for any help i can get.

 

Timing? Air leak somewhere? Sticky float?

 

My guess would be valve lash or timing including the possibility of the cam 180 out or decomp installed backwards.

 

Its in time and I reset my valves.

 

If you just rev the motor it revs fine its when you are on it ridin it when it dose this. Could my jets be of?

 

ya that could be to lean try going up to 170/175 and 3rd clip on needle and did you go up on pilot jets?

 

No i dont have the pilot jets changed.

 

go to a #25 pilot jet and go 2 1/2 to 3 turns out and id go up to a 170/175 jetting and have your needle clip on the 3rd position trust me with that high comp. piston you don't want to run lean and detonate. the 165/170 sounds a little to learn for your motor combonation just my 2 cents tho

 

sounds like your running lean. I dont know what type of jets your running (mikuni or dynojet) but Im running 180/185 dynojets and have a nice tan plug. Try going up on the jets and like someone else said, 25 pilots...keep going up on the jets until you feel it lost power and back down one size. That should get you pretty darn close.