sputtering at low rpm???

[fastrax]

Okay, now i have a 2002 400ex. everything is stock except for an R4 exhaust. my elevation here is between 1100, and 1400 feet. runs like a bear, but in neutral or going slowly, it's almost not there, but it sputters just a little. is this running lean? I have a #42 slow jet, and a #150 main jet. anyone hqave any ideas? Thanx!

ya...first go up on ur pilot and if that doesnt work try going down 1...but go up first cuz it sounds like ur pilot is a little lean

[F-16Guy]

I'm leaning the other way. 42 is a pretty big pilot for a stock motor. Try turning the fuel screw in in 1/8-1/4 turn increments to lean it out, it sounds like it's loading up a little (rich).

[cals400ex]

where is your clip on the needle at? are you running an air box lid? what you can do is let the bike idle for a couple of minutes and then go look at the spark plug and see what color it is. i have a feeling its going to be black and that means your rich. i could be wrong but thats my guess.

[cals400ex]

also, does it only sputter when the bike is cold or does it do it when its hot? mine always sputtered when it was cold outside and all i had to do was move the clip down one notch(needle up one notch) for a richer setting. however, now that summer is here, i need to move the needle back into the factory position because its a little rich now.

[fastrax]

Needle clip is at 3td from the top. this occurs mostly when the engine is warm also.

[Ryan]

You should try Plug Chopping, and work your way from there. If you don't know what "Plug Chopping" Is, do a search and your bound to find something.

To me it sounds like your a bit lean...... Not sure, though.