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  1. #1

    Unhappy SL 750 Mag Piston Overheating

    I have a 95' sl750 and have put on the 3-port fuel pump, put new fuel lines on, cleaned the carbs, put on an oil block plate with premixed fuel, and recently replaced my magnito piston(the old one had a hole in it). When I replace my magnito piston I just honed my old jug. I took it out and tested the ski and ran great, it just would not take off when I gave it alot of gas.(the carbs were set to the factory position).

    I took it out the next day and was trying to adjust the carbs and it would hardly take off and no matter how I adjusted it, it would not run right. I took it home and did a compression test on the magnito and it only had 10psi and the head was rough (like it was getting hot and metal was bouncing around) but no holes through the piston.

    I do not know where to start to troubleshoot but I think this is the same reason the ski burnt a piston before. If you could please give any insight


  2. #2
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Did you replace the fuel lines? If so, did you find a restrictor (brass plug with a TINY hole) inside the return hose?

    Here's some things that can cause a problem as well. http://greenhulk.net/forums/showthread.php?t=82682

  3. #3
    Yes, I did replace the fuel lines and the restrictor. I can see gas go to all three of the piston.

  4. #4
    ph2ocraft's Avatar
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    What's your fuel pressure within the system?
    Restrictions in the fuel valve, pulse line issues etc. can still leave you without enough fuel to do the job.
    Have you checked the crank index?

  5. #5
    Thanks for the advice. Also why would I just have 10psi in the magnito piston and there is no hole(s) in the head? Could it be a bad reed?

  6. #6
    dghal's Avatar
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    basically that cylinder seized,,, that is what the metal look is from,, and the rings are not sealing any more,

    did you clean the filters inside the carbs? sounds like that one could be blocked up.

    you are going to need to pull the jug abd see how bad the damge is,, might get by with another piston/rings and a hone job,, have a machine shop take a look and measure the cylinder for you,,

    and fix the fuel issue

  7. #7
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Quote Originally Posted by jasonhughes67 View Post
    Thanks for the advice. Also why would I just have 10psi in the magnito piston and there is no hole(s) in the head? Could it be a bad reed?
    Bad ring, head gasket, or both.

    Reed wouldn't cause a compression loss.

    Was the piston replaced with the right size rings? What's the ring gap on it?

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