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  1. #1

    1994 SL650 hole in piston

    Hello,
    I just joined the forum. This is a great place to get info on the polaris ski's. I have a 1994 SL650 and no compression on the middle piston. When I removed the piston there was a hole in the top. After reading the forum I understand it could be one of two issues. I am going to replace the Fuel Pump with the new triple pump and replace all my fuel lines and go thru the carburator. I heard it could be the crank being out of phase. How do I check that and if I find out this is the problem how do I fix it. I did not pull the motor out of the hull. I just removed the heads, cylinders, and exhaust. I would appreciate any help with this issue.
    Thanks,
    nwenzler


  2. #2
    Lake Mead Bum & BTLS Mark starflight's Avatar
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    The shade tree way to check the crank index will require you to re-install the cylinders. With one piston at top dead center, the other 2 pistons should be at equal distance down in the cylinders.
    The real method to check it you would need a dial indicator to find tdc of a cylinder, and use a degree wheel to check the other 2 slugs at tdc. Should be 120 degrees apart.

    Welcome to the Hulk!

  3. #3
    Starflight,
    Thanks for the reply. I will reinstall the cylinders and try it that way. I think it is a fuel issue but I wanted to check the crank while I was there.
    Thanks again.

  4. #4
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Welcome to the hulk.
    Looks like Starflight has given you the jist.

  5. #5
    Well, I checked today and it looks like I the Crank is my problem. How do I fix this and do I need to pull the engine. Any help would be appreciated.

    Thanks

  6. #6
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by nwenzler View Post
    Well, I checked today and it looks like I the Crank is my problem.
    How do I fix this and do I need to pull the engine...
    What exactly did you find regarding your crank shaft check?

    If the crank shaft is indeed twisted (which you may want to check again, since it is expensive to fix), then the engine needs to come out, and be taken apart. The crank shaft needs to be repaired/rebuild by a reputable crank rebuilder or machine shop, as some specialized equipment and knowledge are involved.

    There are several crank rebuilders that have been mentioned around here, including Jeff at MidWest Crankworks 1-920-434-3630

    Cost for the crank shaft rebuild could be $200-$400, depending on how many parts need to be replaced (bearings, seals).

    Then you will need at least one new piston and rings ($50-$100ish), and some other new seals and gaskets as you re-assemble the engine.

    The carbs should also be rebuilt, as it is likely that they all need cleaning/rebuilding. Genuine Mikuni kits are the way to go, or you can have the carbs rebuilt for about $50 each, plus shipping and parts. Watcon offers this service.

    If you haven't done so yet, you should download the 1992-1998 Polaris Service manual from here.

  7. #7
    With the cylinders off I reinstalled the Pistons and set #1 (Forward) Piston to top dead center. Then I took a Level across the 2nd and 3rd Piston and 3rd piston was approx. 1/16th to 1/8th in. lower than the 2nd piston. What do you think.

    Thanks

  8. #8
    Moderator beerdart's Avatar
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    Quote Originally Posted by nwenzler View Post
    With the cylinders off I reinstalled the Pistons and set #1 (Forward) Piston to top dead center. Then I took a Level across the 2nd and 3rd Piston and 3rd piston was approx. 1/16th to 1/8th in. lower than the 2nd piston. What do you think.

    Thanks
    How level was the engine/ski???

    You need to check the crank index as described in the manual.

  9. #9
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by nwenzler View Post
    With the cylinders off I reinstalled the Pistons and set #1 (Forward) Piston to top dead center. Then I took a Level across the 2nd and 3rd Piston and 3rd piston was approx. 1/16th to 1/8th in. lower than the 2nd piston...
    That may not be an accurate enough measurement method.

    Better to re-install the cylinders, and check it again.

    My suspicion is that the crank shaft index is just fine

  10. #10
    Thanks Guys. The Ski was not level I will reinstall the cylinders and check it again.

    Thanks again.

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