Low compression on commando 273 with 13000 miles??

SLOPAR72 said

Leakdown test and go from there.... It is odd that all cylinders are down. Whatever the problem is will be abroad. If your leakdown seems OK could it be a valve timing issue?

JW

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In other words your timing chain may have stretched. Turn the motor over until the time marks line up at 0 then pull your dist cap off, turn the crank in the opposite direction, until the dist rotor just starts to move. look at your harmonic balancer. How many degrees do you have. 16 degrees would be a badly stretched timing chain.

A leak down tester is best. but if you don't have one, a little oil will tell you if it's rings or valves that are leaking.

All three of these things can lower your compression.