250EX Engine runs rough

[400ex Magnum]

My friend's wife has a 2001 250ex. The machine has not run completely right since she has got it. It is very hard to start cold and will not idle well even after it warms up. When running hard and backing off the throttle, it will pop upon deceleration. He has tried cleaning the air filter and other basic maintenance items. I know very little about this engine. Does anyone know anywhere to start looking on this machine to see why it runs rough? Thanks for any help.

[redrider808]

i just had to tune a 250ex . go one up on the pilot jet i went to a 40 on it as for the pop could be a lean main jet or its fat try going up or down a jet see if that helps. need to more about the quad like did he pull the air lid . so what has been done to it so far

[Striker49]

Well, if its not ideling right then it sounds like you need to notch up the idle on it. I did on mine after I got it b/c it was idling really low and would die on me sometimes. Same thing with my dads Recon. I would try that and see how it does. I forget where the screw is for it but all you need is a screw driver. Turn it on, turn the screw til it sounds like its ideling good and then give it a test run to see if that helped it out any.
Hope this made sense. :cool:

[400ex Magnum]

Thanks for the info guys. The machine is completely stock. She only has maybe 20 hours on the machine total. We were thinking that it was jetted wrong, but I wouldn't think that it would be that far off from the factory without any mods. We will try uping the idle and checking the plug for rich/lean conditions. I haven't honestly did any real diagnostic work on this machine. I am just going by what he tells me. I have gotten pretty good and making my 400ex purr, but that 229 engine is a different animal in my opinion.

[TRX250EXER]

Well since its under warranty id take the dang thing back and tell them to fix it or I want a different one. And tell them your not paying any labor fees either. the dealer is supposed to make sure every thing runs right before they sell it.

[400ex Magnum]

Good idea, but the warranty is out. She bought it last spring, just doesn't ride it very much.

[TRX250EXER]

Its been six months and doesnt have that many hours on it yet?? which spring?? this year?? they come with 6 month warranty unless you buy the 4 year for 500 dollars. thats what I did. and I am glad. because my shocks are already going out and I bet i'll blow the engine within another 3 years the way i ride it. I beat the heck out of mine!