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  1. #1

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    Sl750 lost mag piston today (running to lean) - help

    I put new OP FA's on my 1995 SL750 and did not get the correct adjustment on the mag side carb. So my worst fear came true and blew a hole in the piston. The other two pistons look good.

    A few questions:

    Do I need to Pull the engine to chage the piston or can I do it in the ski?

    If I can do in the ski how is the best way to pull the Jug?

    Do I need to change all three pistons if I only need one?

    Where is the best place to find pistons (at a good price) and do they come with rings already?

    Any other tips to fix this issue so I can get back out on the lake? My goal is to have it running again in two weeks.

    I am planing on going back to the stock FA until I get my extra set of carbs rebuilt and rejetted.

    I'm sure I will have other questions as I get into this project

    Thanks


  2. #2
    johnsonmtz's Avatar
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    I have Ocean Pro's on my '94 750 and my piston was is great. You should only need to give your high needles an extra 1/2 turn out if your motor is well sealed, you have a 3-outlet fuel pump, and all the fuel lines are in good shape.

    KJ

  3. #3

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    I did open the high's 1/2 over factory spec. on each carb. maybe it should have beed 1 full turn ( I have notice old post today stating 1 full turn, but it's to late). I replaced the fuel pump 3 years ago along with the fuel switch and has run fine since. Fuel lines are in good shape I looked at all fuel lines when I put the FA's on. This is the 6th time out this year, the only difference was the OP FA's.

    At this point I just need help on how to fix the problem, I have not removed the jug yet because I'm not sure if I need to take the engine out of the ski. I don't think ther is any other damage to the cylinder, when I was on the water and felt the loss of power I knew what happened and pulled it out of the water. What was strange is I was on the water about three hours before I started to have problems.

    I have three different repair manuals (clymer, seloc, & Polaris service publications), it look as if I need to remove the engine to replace the piston. Can somebody tell me if this is true? If I have to remove the engine should I go ahead and replace all pistons?

  4. #4
    Polarisitis loonatik's Avatar
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    Yes you can remove the jug without pulling the engine.
    Here's instruction for engine removal, you just need to get the exhaust pipe and its manifold out to get to the jug.
    http://www.shopsbt.com/pdfs/p650750780.pdf

  5. #5

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    Quote Originally Posted by loonatik View Post
    Yes you can remove the jug without pulling the engine.
    Here's instruction for engine removal, you just need to get the exhaust pipe and its manifold out to get to the jug.
    http://www.shopsbt.com/pdfs/p650750780.pdf
    Thank you,

    Can I just replace the one piston or should I replace all three? (other pistons look good I have removed the heads to check)

    I am the 2nd owner of this ski, is there any markings on the pistons telling the size, I have no idea if this has ever been rebuilt, and I want to make sure I get the correct piston.

    I love this ski and want to bring her back to life.

  6. #6
    Polarisitis loonatik's Avatar
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    Quote Originally Posted by candshr View Post
    ... Can I just replace the one piston or should I replace all three? (other pistons look good I have removed the heads to check)...
    If compression is good, no need to replace them.
    Since you're already there, push each piston all the way down and check cylinder wall for scuff marks. May need a bit honing if marks are heavy.

  7. #7

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    Quote Originally Posted by loonatik View Post
    If compression is good, no need to replace them.
    Since you're already there, push each piston all the way down and check cylinder wall for scuff marks. May need a bit honing if marks are heavy.
    No marks on any cylinders, I removed the mag cyl and the bad piston today and to my suprise the cylinder wall is very clean, I will get it honed before putting back in. I now know this has not been rebuilt before (all org. parts), It still has STD size piston, I'm having problems finding a STD size piston, any thoughts were I can get one. I have found all the gaskets, all I need is the piston.

    Thanks again for your help

  8. #8
    Polarisitis loonatik's Avatar
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    Classified Section could be your best bet. Here's one
    http://www.greenhulk.net/forums/show...rts-from-93-02

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