Need help~no power?

[KrazyKeith]

I just got a 02 ex400 a couple days ago. I traded my 93 Grand Cherokee Limited for it. The machine looks great, there is still paint on the lower arms. I don't think it was rode much. This thing really seems powerless up top. It seems to run ok at low r's. I checked the valve clearance's and they were all good. At least seemed to be. I didnt do a compression test yet (I need to get an adapter). I was wonderin if maybe the compression release is stickin on or something. Has anyone had a problem w/ that or anything else. I could use your advise. Thanks in advance .for any help.

[frankiedizzle56]

i dont really know much about engines but maybe your tob end is going

[frankiedizzle56]

top****** not tob sry about that

[KrazyKeith]

anybody??

[Dannys440]

I am just guessing that it might be your jetting,idk if to rich would create powerloss or not.i think if it is to rich the engins doesnt have time to burn all the fuel, which causes it to run bad.

[smr]

when you say no power on top end...do you mean it really falls on its face? Or do you mean it just doesn't have as much power as you would like?

A very common problem with the 400ex is jumping time. If they jump one tooth then it will start and run fine until you get at about 3/4 throtle...then it will fall on it's face. (sounds almost like a revlimiter kicking in)

Another problem to look for is the head gasket. When its the head gasket then the problem will continue to git worse until it simple will not run. Sometimes you can actually hear the sond of air coming through the head gasket at high RPM's. Start the quad and rev it up while running your hand around the head gasket filling for air. If you don't fill air then I would remove the valve cover and check the timing.

good luck

[cals400ex]

maybe you just need to mod it to get more power. i would make sure the throttle cable only has around 1/4 inch of slack in it. if there is much more, the carb won't be fully opening up when you have it pinned.

[hondajoe05]

aren't you suppose to change your gasket everytime you take your head off?

[cals400ex]

well most say yes. however, i have talked to a few shops and individuals who didn't. i tried reusing the same head gasket and i have not once had a problem. just make sure all of the surfaces are clean and free of oil.