Starting Point for Main Jet

[moore020]

I just read the sticky on Jetting and I am curious what would be a good main to start with? The bike is bogging out in WOT in 4th and 5th. The mods are some kind of aftermarket exhaust, JE 10:1 416ex. No other real engine modifications. Any ideas? What main comes stock with an 01 ex?

[mineralgrey01gt]

if its bogging on top end then drop down the main each jet number till it stops then you should be good

[moore020]

What is the numbering system for the main? I don't know what it is out right now, is there an easy way to tell? I assume it is stock.

[mineralgrey01gt]

only way i know of to tell what size main is in it is to unscrew the nut on the bottom of the bowl and take out the main and read it. It will be slightly engraved on the side of the jet

[TL_2ENV]

stock main jet is a 148, pilot is 38

[moore020]

Assume I have stock main at 148 and it craps out at full throttle in 4th and 5th, which direction and how far should I go on the main?

[mineralgrey01gt]

Originally posted by mineralgrey01gt
if its bogging on top end then drop down the main each jet number till it stops then you should be good

^^^^^ plug chop it and see what color the plug is

[moore020]

I mean bog out like the flooding effect. I just did a build to a 416. I think the main is currently stock. Is it safer for a main to be to high or to low?

[mineralgrey01gt]

if its flooding then its rich, pull your plug out and see what color it is, black/wet = rich, white/light gray = lean, light brown/tan = right

[moore020]

Pulled the main jet last night, it is a 152 with a star shaped k to the left of it. Should I get a particular brand to replace it? I think I am going to shoot for a 150. The only difference from before the rebuild is that it now has a foam air filter as opposed to a gauze filter, and it is now a 416.