help with jetting,

[yellow_ho_01]

my friend has a 400ex, we are gwetting ready to put in the jet kit, he already has a K&N filter, and e-series pipe. just wondering wheres a good place to start with the jet kit.

[004exkid]

Search the archives there have been alot of discussions on that. What elevation is he going to be riding at ? Im making mine a 416 with full exhaust and xr cam and 6 vents in the air box lid. I plan on using around a 42 pilot and 165 main and move the needle if i ahve to. There is a good introduction to jetting in the "ex tech" section if you need to play around wiht it.

I would start with a 40 pilot jet and a 155 main. Raise the needle one notch. If it sputters when letting off, drop the main down to a 152. If the 155 runs great try a 158 or 160. A lot depends on the riding. Woods or open trail. Don't forget to check the plug for too lean.
Put some vents in the lid, it helps.