what jets

[jaywoodsrider]

I got a 300ex with a k & n filter and fmf megamax full ehaust. I installed a 135 jet and it would run fine until about 3/4 throttle, then it would start to sputter. Does this mean that i need to go with a smaller jet or a bigger one.

[Bill Fuller]

I would go larger(richer)first then see what happens.

[cals400ex]

i would first take the jets out of the carb and clean the heck out of it with carb cleaner. i actually would think a 135 would be too big in a 300ex with just that megamax and filter, but i wouldn't think it would be big enough to make the bike sputter. are you running air box lid on or off?

[jaywoodsrider]

The airbox lid is on. It runs better with the 122 than the 135, so i think i might need something in between.

[miken]

3/4 Throttle is main jet / Needle jet circuits. Try lowering the needle a slot or 2, if that doesn't help lower the main jet 4 sizes and put the needle back to center slot. Try it out and repeat, lower needle, lower jet etc.
Mike -

[IL400EX]

Best way I've found to find out whether you rich or lean is to take the air box lid on, then run with it off.


Air Box lid on
Runs Better - Lean
Runs Worse - Rich

Air box lid off.
Runs better - Rich
Runs Worse - Lean

I have also used the choke to do this same thing while riding the quad, just get to the point in the throttle where the motor starts to sputter and pull the choke up a little. If the bike runs better then you are lean, if it makes it worse you are Rich.

For what its worth.....

I also think there is an article on jetting in the "Tech Articles" forum

[jaywoodsrider]

Does anybody have a 118 jet, somebody told me to try that.

[cals400ex]

i don't think you will want to use a 118. i believe stock is a 122. the only way you would need to go that low is if your elevation is really really high.