400EX Problems

[TwentyBelow131]

I have a problem that I cant figure out. A few weeks ago the 400ex started to stumble on idle and when you give it light throttle. It slowly got worse until now where it will only run for about 10-20 seconds on idle and it will stall if you give it alittle gas. But they thing is once you get it past like 1/4 throttle and get it into higher rpms it seems fine.

I thought it might be my pilot jet might being clogged. So i took my carb apart and cleaned the whole thing. And yet it is still doing it. I checked my airboot for cracks, because i thought it might have a crack and it would be throwing my jetting off, but it seems fine.

Could it be causes by a bad head gasket, because when it stalles i can feel air shoot out somewhere near the head gasket.
Could this be caused by something electrical like spark?
Any other suggestions would be appreciated.

Thanks guys and girls,

Chris

[TwentyBelow131]

Anyone have any ideas

well i dont no what it is but if i leave my 400ex idel for like a minut and then jest tap the throtel it will stall.

a cuppel months ago my quad wasnt runing good but it does now.

but what mine was doing is wouldnt start or it would start for a second and stall. and off and on i could here it blowing air out of some wair but it runs good now.

[EVOLUTIONracing]

That sounds alot like a bad head gasket. Look for oil seeping from gaskets or black build up around the gaskets.