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  1. #1

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    Yamaha GP1200 piston replace-what to do?

    Hey everyone, new to the jet ski scene and need some advice from the experts. Just purchased a 97 Yamaha waverunner GP 1200 with a blown motor. The motor is already disassembled from the cylinders up. Two of the pistons are pretty much toast and the cylinders are scored but not too bad, just leftover material from the pistons. What I want to know is what the best way to go is. I'm leaning toward boring the cylinders and installing oversized pistons. I've been looking at the wiseco piston kits since their forged and I want it to last. The other option was to re-sleeve with standard pistons but I would be spending more $$$. Next question is where can I get a good deal for these parts if it exist. Thanks in advance to everyones advice and know how. Dennis


  2. #2

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    Boring the cylinders works just fine if you can find a good machine shop to do this work. Riva ( east coast) or Pro-tec ( west coast) Have both done this boring for me with excellent results. Use PRO X piston kits ( best for a reasonable cost ) If the cylinders have never been bored use a .50 mm oversise piston kit. Here is where to get the Pro X piston kit ( do not buy there own piston kits use only the Pro X ones) www.wsmparts.com/wsm-pwc.html Tommy Jordan

  3. #3

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    Thanks for the info 2Fast4u. I went to their site and wrote down part numbers but they don't offer prices. Do you have to contact them for that?. Thanks again for your assistance. Dennis

  4. #4
    Yamaha artisan Cutlass's Avatar
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    Definitely agree. Bore and hone all three cylinders and use ProX pistons. We don't recommend Wiseco pistons in PWCs for number reasons.
    I had a motorcycle shop bore and hone my GP1200 cylinders and I bought my pistons from Pro Marine. Last time I checked, you can't order from Pro Marine online though, you have to call them. And make sure you're getting the non-pv GP1200 pistons....they almost sent me GPR pistons before I corrected them.

  5. #5
    I wanna go FAAAAASTer!! CDW78's Avatar
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    Just trying to learn what I apparently didnt know - boring the cylinder IS different than just installing a new sleeve ? ( IF remaining standard/stock sizes )

    And then, boring the sleeve to match the new piston, is required correct ? :-/

  6. #6
    Yamaha artisan Cutlass's Avatar
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    Yes. Boring is cutting the existing cylinder to a bigger diameter to match a piston that is a bigger diameter.
    Here's a video to give you an idea of what boring a cylinder is.


  7. #7
    How much does the piston kit cost for all three cylinders with the wrist bearings? My cyclinders are getting bored right now just waiting on the shop to tell me what size. I have been trying to find some pricing.

    Is Pro Marine the best price?

  8. #8
    krispaintballz's Avatar
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    Quote Originally Posted by Cutlass View Post
    Definitely agree. Bore and hone all three cylinders and use ProX pistons. We don't recommend Wiseco pistons in PWCs for number reasons.
    I had a motorcycle shop bore and hone my GP1200 cylinders and I bought my pistons from Pro Marine. Last time I checked, you can't order from Pro Marine online though, you have to call them. And make sure you're getting the non-pv GP1200 pistons....they almost sent me GPR pistons before I corrected them.

    I run wisecos. They run good for me. Remember its not the piston its the person setting up the ski for the piston. You have to make sure you run your clearances. I have no problems running them at 190psi with triples and race gas.

  9. #9
    Yamaha artisan Cutlass's Avatar
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    ^^^exactly, correct.

  10. #10
    Pro marine is the best price for the Pro X that I could find.

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