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'93 polaris sl650 top end questions

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  • '93 polaris sl650 top end questions

    I have the following questions:

    1. What is the normal compression range for this
    motor?

    2. I have measured all 3 cyclinders and I get 100PSI, is this too low?

    3. How can I visually tell if the pistons need to be replaced(besides the obvious whole in the top)?

    4. Will replacing only the piston rings yield any compression improvement(and hopefully power!), or is this a waste of money and time?

    5. If I only replace the rings, then I was planning on lightly honing the cylinder walls. Can I still use the standard size rings assuming I just remove the glaze from the cylider walls?or should i go with the .25mm upsize?

    I've worked on engines before, but this is my first attempt at a PWC engine. I am really amazed at how easy it was to tear down the #1 cylider for a visual inspection. This cylider had a water jacket leak at the crankcase gasket. Thankfully it was to the outside and not into the cylinder!

    This is a very informative forum. thanks for any info

  • #2
    I would suspect you gauge is out of calibration if you measured an even 100 accross all three - they should be around 120, but most importnat is that they are even.

    You need to replace the pistons if they show any deterioration or damage, period.

    No, you should not just replace the rings, under most circumstances. Chances are the pistons need to be replaced if the rings do. Yes, you can just hone, so long as the clearnaces all check out ok afterwards. Otherise, you must bore.

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