jetting the carb on my 400ex

[raguirado]

I just turned my 400ex to a 440ex 12:1 compression ratio. I will be using racing fuel min. 100 octane. I have a Big Gun Race exhaust and head pipe. For now I am going to use the stock Carb. I need some help on what jet to use and needle position.

Thanks

[cals400ex]

i am not sure what to tell you. if i had to guess on the main jet, i would say 165. for the needle i am sure in the stock position (3rd) or in the 4th. i am sure you could run a 42 pilot also. good luck and these are just guesses.

Jetting will be affected by so many things (alt, temp, intake, porting, cam etc) that its real hard to just pick a number.

I would think you couldnt go wrong picking up a range of keihin jets from 160-180 and maybe even a needle with a different taper like the dyno jet one in the kit.

Then just start at the largest one you have and start making some jetting runs or tests till its dialed in right.

If you need do a search on jetting and get some info on how to test or read plugs etc.

Have fun, Jettings a blast :rolleyes: :devil: