I've got a 05 900 RMK that I checked compression on, it has about 110 psi. It seems very low, but I'm also at 7,000 ft. Also forgot to have at wide open throttle and checked it cold. The engine is completely stock. I've searched some other threads and various websites, and I can't seem to find a spec for compression on the 900 rmk? Does any got Polaris recomended psi?
Compression check? PSI?
- Thread starter outofstep
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M
Mech Engr
Well-known member
compression
I went through the same thing a while back. The 900 has a decompression device (for starting assistance on that huge motor) associated with the VES system so it will test lower than some 2 cycles without such a device. Mine had 135 psi cold, throttle open, both plugs out at 2200 feet evelvation. At 6500 (dealer) it had just a touch less...maybe 130. Most imporatnt is that both are the same. Might want to try a different guage too. I had one go bad on me a while back adn it was reading about 50% of what it should have. Plugged hose or schrader valve etc.
Big John
I went through the same thing a while back. The 900 has a decompression device (for starting assistance on that huge motor) associated with the VES system so it will test lower than some 2 cycles without such a device. Mine had 135 psi cold, throttle open, both plugs out at 2200 feet evelvation. At 6500 (dealer) it had just a touch less...maybe 130. Most imporatnt is that both are the same. Might want to try a different guage too. I had one go bad on me a while back adn it was reading about 50% of what it should have. Plugged hose or schrader valve etc.
Big John
I tested it today after it warmed up and wide open throttle, same results 110 it seems pretty low, but I'm not gonna sweat it probably won't ride much this winter and it still runs great. The gauge is my buddies and it brand new but somewhat of a cheapy
If it starts easy and the compression reading between both holes is within 10% it is fine.
The problem with compression gauges is that they are not exact. They are a differential device. So your number doesn't relate to anyone else's number. I have 3 gauges and they all read different from each other... as much as 35lbs between the high and low one.
And they will read different from day to day depending on ambient conditions.
sled_guy
The problem with compression gauges is that they are not exact. They are a differential device. So your number doesn't relate to anyone else's number. I have 3 gauges and they all read different from each other... as much as 35lbs between the high and low one.
And they will read different from day to day depending on ambient conditions.
sled_guy
compression
My 900 at 6500ft was 120 so with different tester you are probably close,like said above if cylinders are close to the same you should be ok
My 900 at 6500ft was 120 so with different tester you are probably close,like said above if cylinders are close to the same you should be ok
900
I should have mentioned,if you do not have them already you should put in 06 pistons.
I should have mentioned,if you do not have them already you should put in 06 pistons.
both cylinders are pretty much exact, it starts 3rd pull every time. I have confidence in it. engine miles unsure, previous owner I know rebuilt top end when he had it sleds got 1400 ish thanks
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