400ex Carb Question, ASAP

[James Parent]

I tried to change my jet and the whole Needle jet holder started unscrewing.. since i didn't feel like taking it off my quad i just took the whole thing out

Well then the actual needle Jet fell out, and i don't know which way it goes back in

there is like a pointy sided circle, and a rounded sided circle, which one goes up? ( up = closest to the needle) My bike is apart and help is greatly appreciated.
james

[MIKE400EX]

The conical side goes up (guides the needle) and the rounded side goes down. The main jet "holder" seats against the rounded side.

[James Parent]

Thank you mike :)


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[cals400ex]

while your at it, make sure you adjust the needle jet holder correctly. make sure you can see about 3 threads on the needle jet holder when the locking nut is tightened down. if you happen to skrew that needle jet holder in all the way, the power sucks. i don't know if it is from how the needle sits in there or if it is becasue skrewing it in all the way actually raises the mainjet and it is sucking for fuel.

[James Parent]

yea, i think its 3 threads.. i just made it so that the main jet was half way down near the bottom

thank you btw

[MIKE400EX]

Actually, you're supposed to tighten the jet holder against the needle guide (this will seat it) and then lock the jam nut so that nothing comes loose. You'll never get the thing jetted right if the needle guide has room to move up and down - that'll have the same effect as if the needle could move up and down freely.

[cals400ex]

Originally posted by MIKE400EX
Actually, you're supposed to tighten the jet holder against the needle guide (this will seat it) and then lock the jam nut so that nothing comes loose. You'll never get the thing jetted right if the needle guide has room to move up and down - that'll have the same effect as if the needle could move up and down freely.



so your saying to adjust the needle jet holder all the way in?? i did this once and i had a huge power loss. i lost more power doing this than i did with my throttle cable adjusted ALL the way in so the carb wasn't openiing up fully. now i am confused :confused:

[MIKE400EX]

Must be some cornfusion here!? The holder is about 1.5" long and the the main jet screws into the bottom. The needle guide is about 1/2" long, a hole thru the middle, tapered c'bore in one end, and kind of rounded on the other end. The OD has a step/band on it. The needle guide goes in the carb body first (ends up on top) and then the holder is screwed in. If the guide is upside down it will not run very well at all.

[cals400ex]

Originally posted by MIKE400EX
Must be some cornfusion here!? The holder is about 1.5" long and the the main jet screws into the bottom. The needle guide is about 1/2" long, a hole thru the middle, tapered c'bore in one end, and kind of rounded on the other end. The OD has a step/band on it. The needle guide goes in the carb body first (ends up on top) and then the holder is screwed in. If the guide is upside down it will not run very well at all.


oh, what you call the guide i call the needle jet.