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  1. #1

    Red face Rebuilding a 97' gp1200 piston matching

    I'm new and this is my first jet-ski project. It had a bad #3 piston and i ordered a wsm rebuild kit. The question is do i need to match these to the stock weight pistons. The .5 over wsm's are 15 grams heavier and that's too much to remove from the new piston's. Does this 3 cyl. need bob weights on the crank to balance it. Will the heavy pistons cause problems? thanks MKing

  2. #2
    Yamaha artisan Cutlass's Avatar
    Join Date
    Oct 2010
    Madison, WI, USA
    Its best to use 3 pistons that are the same size and from the same manufacturer and that's what I would do. But you can get away with mismatching to a certain extent. I think you can get away with using 2 std bore OEM pistons and one .5 over WSM without much issue. But that about the max I would be "comfortable" with.
    15 grams does seem like a lot to remove to balance out the piston weights. I'd probably just leave it alone and run it.

  3. #3
    Banned User
    Join Date
    Jun 2010
    Milwaukee WI
    Can you get a .5 over OEM piston? The weights might more closely match. The wiseco pistons are also considerably lighter.

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