jetting Question

[St Louis 400ex]

i have a 400 ex with a e sieres slip on and a k&n power lid I installed my new jet kit and i am running a 160 m jet the bike runs great but i did notice i have to give it a little gas to start and at Idle she is not as smooth as she was at stock but their is not that big of a diffrence. The atv is just runnig a little off not much but when you hit those rpms she runs great i hope this all makes scene i tryed my best to explain. I do have just a little puff of black smoke when i hit it but not much should i go down to a 155 or is it something eles thank to any one who can help

[dunedragger]

You sould not judhge the way your bike is running to see if your jet is the right size, although it can be an indication to a wrong sized jet it is only a signal. The best way to check your jetting is to follow the suggested jet size for your application, then run your bike for about a half an hour, get going full throttle in fourth gear and hit the kill switch, take the plug out and see what color it is. Light brown with a white hint is good, too much white and you have got too much fuel, black tip and you dont have enough.

[Samson]

Originally posted by St Louis 400ex
i have a 400 ex with a e sieres slip on and a k&n power lid I installed my new jet kit and i am running a 160 m jet the bike runs great but i did notice i have to give it a little gas to start and at Idle she is not as smooth as she was at stock but their is not that big of a diffrence. The atv is just runnig a little off not much but when you hit those rpms she runs great i hope this all makes scene i tryed my best to explain. I do have just a little puff of black smoke when i hit it but not much should i go down to a 155 or is it something eles thank to any one who can help

It's hard to say on jetting. Have you changed the needle clip position? Have you vented or removed the lid? What elevation? What's riding average temperature?

You want to know my test? Put in a jet and see how easily it wheelies in 3rd! Seat of the pants approach! ;)

[St Louis 400ex]

it wheelies great in first and second and it is snowing today i have not try it in 3rd can not get much traction is a little puff of black smoke normal i live in st.louis and it is like 3,000 the bike is running great and idles fine but at idle if i floor it really fast it dies i do not think it did that be for i am just trying to dail it in best as possible

[PunkA$$]

Originally posted by dunedragger
Light brown with a white hint is good, too much white and you have got too much fuel, black tip and you dont have enough.



Don't you have that backwards. Like white means too lean (not enough fuel). And black is rich (too much fuel)??

[cals400ex]

Originally posted by Punk*****
Don't you have that backwards. Like white means too lean (not enough fuel). And black is rich (too much fuel)??


yes, he had that backwards. i think a keihin 155-158 should be about right. in the winter, i would move the clip down to the 4th position. i would also install a larger pilot jet such as a 42. it may start easier.

[dunedragger]

Thank You for the correction. :confused:

[Samson]

Originally posted by St Louis 400ex
it wheelies great in first and second and it is snowing today i have not try it in 3rd can not get much traction is a little puff of black smoke normal i live in st.louis and it is like 3,000 the bike is running great and idles fine but at idle if i floor it really fast it dies i do not think it did that be for i am just trying to dail it in best as possible

Just rejetted mine today. 160 dynojet at 3000ft and about 55 degrees. Think I have the needle on the middle slot if I remember correctly (3rd?).