Low RPM sputter

[hardtime]

I'm getting a low-rpm cut-out on my 400ex. The best way I can explain it is when your going up a hill and ya gun it and then ... blah blu bah... downshift and it takes right off. It does it in first on a dead stop to full throttle also so ya sorta get the picture. Any help is appreciated. BTW, its all stock.

[01 250exman]

if it is all stock it might be bad gas or your air fillter is way to dirty.

[cals400ex]

my friend had a similar problem with his 2000 400ex when he would go up steep hills. we noticed there was a problem because when he rides wheelies, gas would leak out a black tube coming from the carb. when we lifted up the fourwheeler and rested it on its grab bar, gas would pour out of this tube coming from the carb.(when the gas was on) there was a problem with the float bowl. he just had a 2003 400ex float bowl installed. the 2003 float bowls are different than the 2000's. he now has no problem with going up steep hills or gas leaking out of the tube off the float bowl.

[01 250exman]

:huh it's suposed to come out when the quad is on the grab bar if the gas is on. ;)

[stocktires]

my 300ex does the same thing (leaks gas from float), but it has no trouble up hills or doing long straigh up wheelies


1000th post

[hardtime]

It does it on flats also, not just hills. That was just an example. I've cleaned the air cleaner and even put a new one in from No-Toil. Same ol' sputter at the low rpm/power situations.

[cals400ex]

sorry i did not explain my post too well. yes they all leak when put up on the grab bar. mine and every other i have seen do this but drip, drip, drip etc. on his it pours out. it will leave a puddle in a matter of a couple of seconds. all others i have seen only drip slowly. he had a float bowl put in off a 2003 400ex and not it is like mine. it just slowly drips out when put on the grab bar.

[jwisniew]

ya wtf? my 300 does the same thing. when u gun it it suddenly loses power and starts sputtering so that u can only go 1/4 throttle. One time i opened my gas cap while it was doin it and it seemed to help.

[cals400ex]

most of the time you may just need the float adjusted. i am not sure if you can adjust the float on the 300 though. i am assuming that yours is jetted correctly too.

[yamaha1470]

Originally posted by jwisniew
ya wtf? my 300 does the same thing. when u gun it it suddenly loses power and starts sputtering so that u can only go 1/4 throttle. One time i opened my gas cap while it was doin it and it seemed to help.

maybe the tube out of the cap is clogged

[DantheEXman]

Dude. i have the same problem with my 400ex. When it is in neutral, and i gun it. it sputers once then takes off into the rpm's. I am guessing its the pilot jet. I poped in a 42 pilot and i have the SAME problem. Does ANYBODY know how to fix this??? Thanks

[eldoexrider01]

when did they change the float bowls for the 400ex???? and since u changed ur pilot now and it cuts out is it cuz ur gettin too much fuel????

[hardtime]

Anybody got any remodies to why or how to fix the sputtering on my ol' 400EX? Its always at low RPMs and at power needin' situations. Any help is appreciated!

Signed,

SpUtTeRiN'

:D