Need to rejet the carb..I have an FMF powerbomb header, Hmf performance pipe, a k&n filter with no lid, at 580 ft. Above sea level, its a '99 400ex BTW, and a big gun rev box if that makes a difference for some reason. I want to know what size main and what size pilot jet I should use. Thanks in advance

 

You might move this question to the Honda forum....I don't this area ( sports ) gets much attention.....

 

of "carb kit" manufacturers have a website where you can post your bike and the changes you have made and they will make recommendations on which kit you should buy to get the best performance. I number of years back I ran into this with a Kawi quad I had and went to the UNI site and gave them my info and bought there kit. It cost about 75 bucks but included everything I needed and a quanity of jets sizes to experiment with. Excellent instructions and YES it worked out great. Machine ran very well, started better in the cold, and showed and increase in power and spark plug was colored perfect.