Is my 400 jetted correctly?

[Catsgot9]

On my '02 400 I installed a HMF slip-on, along with a pro-design air sysytem. The HMF came with a 172 main jet, and they said to use this along with moving the needle I believe one notch down. I did this and the thing wouldn't hardly start, fouled two plugs. I then dropped down to a 160 main, it started a little easier, but was backfiring alot. Then I dropped down to a 155 main, it only backfires until it gets really warmed up then it quits. Also the airbox cover is still on, and has not been modified. Does it sound like I am still to rich, to lean, do I move the needle again? You guys have any ideas?

dont change the main if u are having trouble starting. the main controls 3/4 to wide open thottle. Change the pilot to a 42 and try that

[F-16Guy]

Yup, pilot jet. Get a 40 and a 42. A 42 might be a little rich for a stock bike, but you can try it and go down if needed. 155 sounds O.K. for the main. I run a 165 in my 416, so I know you don't need a 170. More fuel doesn't always mean more power.