Ok, last week I put a deposit on a 2011 RZR 800 with 1100 miles, at a dealer. The bike looks in really nice condition and sounds good. My only condition was on a good compression test. I had the dealer do a compression test for me. They just called and said the compression was 150/155. I questioned them because the manual states compression should be between 165/185. They told me it is just fine and they are very confident in the motor. Is that compression ok, or should I be worried? Again, rest of bike is in mint shape, and it does appear to run normal. I'm not sure if it was done hot or cold, open or closed throttle, so it's really hard to trust those numbers unless I do it myself.
jquickie
several variables as to how they did the test. most important is that they are close to each other, which they are.
150 is minimum spec... So the numbers AREN'T Good...
The numbers being close means both cylinders are very close to minimum compression specs !!!
The numbers being close means both cylinders are very close to minimum compression specs !!!
And you want the testing done with a compression gauge that screws into the spark plug hole. Not one of those tapered rubber plug types.
You want the test done at WO throttle.
Then use a syringe to squirt about 3 cc of motor oil in each cylinder, turn the motor over a few times, and then do another WO throttle test.
The oil will fill the void above the top compression ring. Any differences between the "dry" and "wet" test will tell you about scored cylinder walls, worn rings, or both.
If the results of both tests are the same, it could be the motor just needs a valve job. Remember the motor only has intake valve seals. Given the RPM these motors run at, wear on intake valve stems, valve guides and valve seals seems to occur more quickly than automotive engines.
Just thoughts,
Pirate
You want the test done at WO throttle.
Then use a syringe to squirt about 3 cc of motor oil in each cylinder, turn the motor over a few times, and then do another WO throttle test.
The oil will fill the void above the top compression ring. Any differences between the "dry" and "wet" test will tell you about scored cylinder walls, worn rings, or both.
If the results of both tests are the same, it could be the motor just needs a valve job. Remember the motor only has intake valve seals. Given the RPM these motors run at, wear on intake valve stems, valve guides and valve seals seems to occur more quickly than automotive engines.
Just thoughts,
Pirate
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