jetting

[PismoLocal]

i need some quick help, i just put a curtis sparks exhaust on my 400 and i was wonderin if i need to get bigger or small er jets on it. It was already jetted for a slip on and now i put on a fullsystem and when i rev it up to 3/4 throttle fast it back fires and shoots flames out the back when its reving back down. thanks i appreciate the help.

[bwamos]

You need larger jets. You're getting better airflow so you need more gas.

Go up a few sizes, to start with. You'll probably have to raise the needle 1 spot too (clip down).

[TRX520RIDER]

yea deffenatly up that jet your adding more air flow coming out of the engine you need more gas to run your power plant now and if it still back fires try jetting it over and over till you get it right and if you dont like the flames get a spark arrester