COMPRESSION TEST 90LBS?
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To accurately measure compression, you have to disable the decompressor lever on the exhaust cam. This device allows easier turning by the starter motor, and disengages via centrifugal force once the motor starts.
Seems to me though, 120 is what you should get without disengaging if stock cams are installed, if memory serves me correctly. With you getting only 90, I would suspect something wrong, and remove the head cover to disable the decompressor for a more accurate test. When you remove the head cover, you can quickly and easily check valve clearances while you're at it - it could be a valve that no longer has clearance is being held open slightly, causing the compression loss. Clearances decrease over time.
Seems to me though, 120 is what you should get without disengaging if stock cams are installed, if memory serves me correctly. With you getting only 90, I would suspect something wrong, and remove the head cover to disable the decompressor for a more accurate test. When you remove the head cover, you can quickly and easily check valve clearances while you're at it - it could be a valve that no longer has clearance is being held open slightly, causing the compression loss. Clearances decrease over time.
#4
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yes, the head must be installed to measure and shim. I advise getting a shop manual, allthough somebody has a link to a website with detailed instructions, somewhere.
When you pull the head cover, you will see the cams. measurements must be taken @ tdc of compression stroke. if you need to adjust, get the detailed instructions with torque specs and stuff. If they never have been adjusted, and you have considerable hours on the motor, I'd just about bet an intake valve has no gap left.
When you pull the head cover, you will see the cams. measurements must be taken @ tdc of compression stroke. if you need to adjust, get the detailed instructions with torque specs and stuff. If they never have been adjusted, and you have considerable hours on the motor, I'd just about bet an intake valve has no gap left.
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