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camerontech, Auto Mechanic
Category: Motorcycle
Satisfied Customers: 508
Experience:  diagnostic auto tech
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I have a 2011 Polaris sportsman 500 HO. When I do a dry

Customer Question

I have a 2011 Polaris sportsman 500 HO . When I do a dry compression test I have absolutely zero compression . When I put half an ounce of oil in the compression reads good . What are the possible and likely causes of this ? Thank you !
Submitted: 2 years ago.
Category: Motorcycle
Expert:  camerontech replied 2 years ago.

hi there,

a couple possibilities come to mind.

Have you flooded it at all? If you flood the system, you can loose your compression and by adding oil you now helping the rings seal again.

and than you have to find out why it flooded.

If its not flooded than it could be a ring problem, and again the oil is heloing to seal the engine. in this case, the engine will have to be torn down.

I highly doubt that it is a valve problem as a burnt valve cannot be sealed by adding oil.

I hope this helps you in the correct direction.

Since this is a 4 stroke there is no reed system.

Customer: replied 2 years ago.
The quad does not run at all. I picked it up as a non running project. It had zero power (no lights, display, electric start) at all upon purchase. Traced that to a bad connection at the fuse box. Upon turning over it would not start at all. I checked and confirmed lots of Spark. Fuel is pumping to the carb and the carb was clean. Checked compression and there Was absolutely zero. Maybe 2psi lol. Added oil and checked again and it jumped to 70. Called dealer. They said most likely a bad valve...
Customer: replied 2 years ago.
They said possibly rings but i should have low compression not no compression if it was rings...
Expert:  camerontech replied 2 years ago.

Ive had small engines flood to the point of no compression. i would try a little bit of oil to get the compression back , put a clean spark plug in and see if it starts. either way if its a valve or rings, than you will be rebuilding the engine.


Customer: replied 2 years ago.
Could it be anything else besides valves or rings? Something worse or simple?
Expert:  camerontech replied 2 years ago.

compression is always mechanical. the oil is providing a temperary seal. the only way it will be simple is if you flooded it. than the oil will seal the rings again. the simple fix for that is to turn the engine over with the spark plug out and a bit of oil in the plug hole. Yes it will be a little messy but it will expell the excess oil out. than pop a clean plug back in it and try to start it. you will have to do this a few times as the plug will likley foul a few times. if its just flooded than it will start with a bit of efffort. if its a valve or ring problem , than its an engine teardown unfortunatly

Expert:  camerontech replied 2 years ago.

have I satisfied your question?. please leave me a rating at your convienience, and if you need any more help send me a message.

thanks, cam