jetting for 400ex carb on 300ex

[buster369]

what jets should i run in a 400ex carb on a 300ex? Do i only need the needle jet and main jet? or more. I have many modds so hopefully someone has engine modds with one. Thanks

[cals400ex]

the people i talk to run around a keihin 148-150 mainjet. i am not sure if they run the needle clip in the 3rd or 4th position, but i would guess the 3rd. many do install a 40 or 42 pilot jet too for easier starting. try a search. this has been discussed a few times.

I'm running a 155 main, 3rd position on needle, and a 42 pilot. That's in Illinois temps too.

[countypark]

I had better luck with the 300EX carb.

[Aceman]

I've read that Mickey Dunlap of FST runs the 300 carb on his big bore motors.:o I've also heard you lose throttle response going with the 400 carb.

Throttle response is 3 times better with the 400ex carb and you gain tons of power! It took a while to get the carb dialed in, but it was well worth it. I think I ended up putting a different needle in it too, but I don't remember which one. If I have it out sometime I will let you know.