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Thread: Minimum Compression Required?

  1. #1

    Question Minimum Compression Required?

    I don't have much experience with snowmachines, but I own a 1999 Indy Trail (550 CC, fan cooled, 2500 miles) that has compression checked at 100 psi in each cylinder. I am wondering if it is alright to run this machine at this compression level, or am I running it on borrowed time? I don't want to have it rebuilt if it is not necessary but I don't want it to blow up and cause more damage later, either.

    Thanks in advance for the advice!

    Matt

  2. #2
    Member mod elan's Avatar
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    My experience is you can have three different gauges and come back with three different readings. If the gauge is a good quality one then 100 psi is the lowest I go on a 2 stroke small engine. A couple tips to keep in mind. The cylinder psi should be within 10% of each other. If they test out equal then you probably have some more life left, but keep in mind it is getting sloppy in there. One way I started testing compression is to do it on a hot motor. You can have good compression on a cold engine, but check it when everything is at operating temps and it may be lower. Run it around and get it warmed up, shut it down, pull the plugs, and test each side with the ignition off and holding the throttle wide open while pulling it 5-6 times. This should give a more accurate reading of whats going on while its running.

  3. #3
    Moderator AKmud's Avatar
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    I agree....100psi is what I have heard as a minimum. Seems like it was around 140 to be optimal.
    AKmud
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  4. #4

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    Thanks a lot, guys! I appreciate the info.

  5. #5

    Default compression

    100 psi in each cylinder will run a 2 stroke. Down around 80 psi it will start cold and run but not want to start warm and dog out when warm. I believe the sled you have has iron sleeves (altough I could be wrong). A quick pass with a cylinder hone and a new set of ring and you will be back in business. About 125psi is the norm. Pump gas will not compress much more than that without detention. I'd run it a 100 psi until you notice a change. Try a round of good synthetic oil to see if you ring will lossen up a bit.

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