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Fresh rebuild no compresion! Going by rings need help!

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2007 yz250f. Fresh top end rebuild

Brand new OEM head, piston, rings, cylinder, valves.

Only has 40 pounds of pressure with cams removed and all valves closed!

Any ideas why I have so much compression going past the rings? Did a leak down and you can hear the air going into the bottom end. All rings are clocked exactly as the manual says need some help..

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You can't do an accurate compression test without the cams installed as air can not be drawn into the cylinder to be compressed!

Edited by Vintage Not Pimpage

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Yes I soaked the piston with the rings on it before installing and coated the inside of the cylinder very well. Also I can kick it over without any cams in it which is very weird...

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You need the cams in. If it's got no air in then it's beginning the compression stroke with vacuum. Never heard of this approach. Keep going.

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Can you confirm that the position of the rings are correct?  Did you clock the rings?  Just bringing it up so you verify before installing the cams and check compression.

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Jst reading the post here and i take it not clocking the rings correctly you will have low compresion is that rite huh wondered about thwt one

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Jst reading the post here and i take it not clocking the rings correctly you will have low compresion is that rite huh wondered about thwt one
Oh ok thanx then

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