compression problems

[T-dog 007]

I have 98 king quad. It has difficultly staying running. When I crank it over it makes two different distinct sounds. One sound is it turning over very fast (and will not start). While cranking over, some times it will change from turning over fast to turning over slow and then will start. When running, it seems to make top end noise. I took a compresion test and while it appears to turn over fast, I have very low compresion. When it slows down, the compression reads about 120. I'm hopping some one can tell me what the problem might be.

[GPracer2500]

I'm going to guess that a valve is not doing what it's suppose to either because the auto-compression device is malfunctioning or some other reason. The auto decomp device is actuated by the camshaft. I wouldn't not attempt to run it in that condition. If you force it to run while a valve is not spending the normal amount of time resting on its valve seat then it can overheat and could break off in the cylinder. Or, it might stick open at the wrong time and contact the piston.

I'd pull the valve cover and take a look.

[T-dog 007]

IT does have a decompression valve but it is manual. I think it is just used to pull start it(with the rip cord). I'm pretty shure it doesn't decompress automaticly. I should tell you that it is a 300 king guad. I have pulled the motor but have not opened it up yet. is there some way to test.

[GPracer2500]

Ahh. Nonetheless, it still sounds from your description that a valve is staying open when it shouldn't. I'm not specifically familiar with that engine so I don't know what tests there may be to zero in on the problem.