my 400ex wont start in the cold. when bought my slip on exhaust (fmf megamaxII) and my K&N air filter i also bought a jet kit which had the main jet adaptor, needle and no pilot jets. after i paid to get it re jetted it ran great. i have a 146 main jet with the needle on the 3rd groove(mid groove). then i needed to have my valves adjusted and since it would be torn apart that i would have my honda dealer install a hot cam stage 1. after i got it back it still started fine. here is my question/ problem! the more i read it sounds like i should have rejetted for the cam as well? is this true? i live in vermont, so my altitude is like 0-5000' or there about. also if i put a 42 pilot jet in to cure the cold starting, do i have to put the stock pilot jet back in during the warm months, or will the 42 be fine?

 

Put the 42 in . Then just use the mixture screw to fine tune the idle mix. The jet is the coarse adjustment, and the mixture screw is the fine adjustment. When summer comes around, you just need to screw in the mixture screw (leaner), until it runs right, usually a 1/4 turn is all thats necesary between summer and winter.

Heres a good article on jetting, that will help you get the mixture screw set correctly, and help you trouble shoot lean/ rich questions.

here

Are you still using the lid on the air box or is that off?

 

The lid is still on. Since its sunday i have to wait to go to my honda dealer to get the jet. i dont know if i should even try to jet my carb by my self. i now know where the pilot jet is, but i didnt realize i would have to "fine tune" the carb after installing. i really dont want to burn my motor up because im to stupid to rejet my own carb. i would love to know how to, but the price of learning isnt worth a motor to me. im sure i will mess around with it since this next week is supposed to be high 30's and low 40's. i will let people know how it comes out