polarisnewbie Posted December 8, 2012 Share Posted December 8, 2012 Hey so newbie right here. Just picked up a 2005 polaris 340 classic. It has 2815 miles and looks to be in excellent condition. Starts up first pull super easily when cold. Then, I checked the compression.... My gauge is reading 110 and 107 psi. To me this seems low. Any thoughts. Also could it be that it hasn't been driven for over a year, and that their isnt much oil or gas in the cylinders... thanks, any comments appreciated. Link to comment Share on other sites More sharing options...
Viperules700 Posted December 8, 2012 Share Posted December 8, 2012 The compression Is defiantly low, proving your gauge is calibrated. I find people disconnect the speedo guage and ride without putting any miles on. The sled could have thousands more miles then it is showing. It is telling you the rings are worn. You need to do a leak down test, to see how much pressure is being lost. I would say you need rings, pistions, new gaskets and verify the crank tolerance. Hope you didn't pay alot for the sled. Good luck. Link to comment Share on other sites More sharing options...
snocrazy Posted December 8, 2012 Share Posted December 8, 2012 Just a thought... did you check compression with throttle wide open? Link to comment Share on other sites More sharing options...
Viperules700 Posted December 8, 2012 Share Posted December 8, 2012 Just a thought... did you check compression with throttle wide open? Maybe do a second check. Run sled on a track stand. Run it until hot. Let it cool overnight and repeat the check. Rare to see the readings so low, but very close like that. Normally see 110 in one and 130 in another. Something is off. Link to comment Share on other sites More sharing options...
skidooboy Posted December 9, 2012 Share Posted December 9, 2012 too many variables to say if something is wrong. ALOT depends on the guage you are using, (high quality snap on, mac, matco ect... or low quality canadian tire, princess auto parts,no name cheapo gauge ect..) each sled mfg has it's own spec for compression, some are as high as 150 psi, others as low as 100 psi. motor, and head design play a BIG ROLL, in compression numbers. if both cyls are within 5% of one another you are probably ok. if they are off by more... you should look into a leak down test, for further insight. ski Link to comment Share on other sites More sharing options...
Wildbill Posted December 9, 2012 Share Posted December 9, 2012 They are not a high compression engine to start with. Gauges mean lots I have two identical gauges different reading by a lot! Unlikely both cylinders fail equally at once especially on a fan cooled with different temperatures at the cylinders. Does it idle well? If in doubt pull the cylinder heads and look for scores. Most likely it is a tester issue. Link to comment Share on other sites More sharing options...
f3 800 Posted December 9, 2012 Share Posted December 9, 2012 I think you're fine. This engine is not high compression. Try a different guage and see if its the same. Link to comment Share on other sites More sharing options...
blue er Posted December 9, 2012 Share Posted December 9, 2012 i find with most 2 stroke sleds as long as your 100psi and up good to go, was the compression test done on a warm engine with wot?, did u put a couple drops of oil in the cylinder and retry ? Link to comment Share on other sites More sharing options...
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