Need some Jetting help....

[thumper250x]

I have a 416 high comp piston with a hot cam stage 1, a full Hmf exhaust and im havin trouble with the jetting..any suggestions? i currently have a 42 pilot and a 180 main, but earlier today i had a 170 main and it was backfiring when i let off the throttle to slow down.. Should i have went up or down??? anybody have ne imput on their jetting?

[thumper250x]

Anyone???????

[James Parent]

Down, a lot try a 155 Dyno jet, or a 160 Keign??SP i think that should be closer.. you don't have your airbox off do you?

[cals400ex]

with what you have listed there, i would start with a 158 keihin mainjet and a 42 pilot jet with the fuel skrew turned out 2.5 turns.

there is a good chance you will get a little backfiring with an open exhaust and the stock carb. i think it has to do with the pilot jet and the needle. however, i wasn't able to find a needle for the 400ex besides the ones that come with the jet kits.

[thumper250x]

Thanx a lot, i have holes in the airbox lid and thats it.