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Wayne S.
Wayne S., Motorcycle Mechanic
Category: Motorcycle
Satisfied Customers: 1255
Experience:  Experienced and Licensed Motorcycle Mechanic - all sizes and brands welcome.
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I have a polaris 50 scrambler i bought that was not running.

Customer Question

I have a polaris 50 scrambler i bought that was not running. put a new battery in, put clean gas in, tryed to fire it up with no luck. checked spark and it had spark. cleaned carb, tried starting again no luck. went a bought a compression tester at Harbor Freight, read 60psi, pulled top end and piston and cylinder were scorched. bought new top end put a little oil on rings put it back together and still 60 psi and still wont start.
Submitted: 1 year ago.
Category: Motorcycle
Expert:  Wayne S. replied 1 year ago.


you still have cylinder leakage problems. You should be getting a compression reading over 100 psi and up to 135 possibly.

Did you have the cylinder rebored or honed or measured to determine the piston to cylinder clearance? Is the head gasket okay?

Something is keeping the compression low. check compression with the throttle wide open.

Is the piston coming up to the top okay?

Let me know what you can find.


Customer: replied 1 year ago.
I will check to make sure that the piston is coming to the top OK. But to answer your question of the top end i installed a new cylinder, head, piston and rings. Whats weird to me is as scorched as the cylinder was and the grooves in it and to put a new top end on and did not improve the compression at all.
Expert:  Wayne S. replied 1 year ago.

Something seems off with that compression, is the gauge working normally on other engines? The piston should come right to the top

of the cylinder. If you add a few drops of oil in the plug hole the compression should come way up if the rings are leaking.