i just put a FMF silencer on with my dg header and it ran good for a while but then started bogging out and then after a while it just wouldnt start so i think i blew the piston rings or piston and after i get that goin wat size jet should i put in it i think that is why it was running bad

 

Did you check the spark plug? If you didn't, try putting a new one in.

 

If you put on a new pipe and silencer, you need to rejet so your quad doesn't run too lean.

 

there is alot of factors like elevation and tempature, but i would try a 280, do a plug chop and see where your at..Did you buy your pipe new? if so it should have came with some jets(most pipe companies send them, not sure about fmf though)..But like the above stated do not ride it until you rejet becuase your probably riding very lean right now..A lean condition will kill a top end almost as fast as a air leak..