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  1. #1

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    Pro 785 rebuild , questions

    Rebuilding a 785 top end , questions
    A , any way to check if crank is in phase with motor apart ?
    B wisco or WSM 750 pistons ? ( boat will be used closed course racing ) cleaned cylinders with acid , good to go
    C heard about welding the flywheel , really needed ??
    D any other tips \ tricks ??
    as I'm the only Polaris that shows up at the races , trying to keep the 785 polaris name alive !!


  2. #2
    ujustlost's Avatar
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    I run the WSM 750 pistons in my 785---I wouldn't weld the key to the flywheel---the motor does not have to be put together to check phase, its easier when the motor is put together but ideally you would want it apart so you can put the crank on the truing stand, unfortunately its tougher this way but also more accurate than checking while the motor is assembled

  3. #3
    I'D RATHER SWEAT THAN SHIVER hyoctane23's Avatar
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    Ditto on the WSM 750 pistons and rings. I have not heard of welding the flywheel either. Maybe welding the crank together to keep it from ever slipping phase? Might want to let the professionals do that...

  4. #4

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    thanks for the advice on the WSM pistons , On the flywheel welding , suggested that I weld the flywheel together ( were the rivets are now ) and of course get in balanced

  5. #5
    I'D RATHER SWEAT THAN SHIVER hyoctane23's Avatar
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    Not sure if required but I would either find another 785 piston or replace them all with new 750 pistons....from what I remember, the 750 pistons weigh less than the 785 pistons. Not sure if they would cause any vibration issues or maybe the weight difference isn't enough??

  6. #6
    skigolfnut's Avatar
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    the way I was able to check crank indexing is when it is together, I took the spark plugs out and put a pencil down the mag hole, when the piston was all the way at top dead center, I put a mark on the drive shaft coupler with a magic marker on the very top, then on the center cylinder when it was at top dead center I put another mark on the drive shaft coupler, then again on the PTO cylinder, same thing, you end up with three marks on the drive shaft coupler that should be 22*apart or equal spacing all the way around, if one mark is closer than the other 2 the crank is out of index,

  7. #7
    ujustlost's Avatar
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    Send one piston to top dead center and the other two should be at the same height

  8. #8

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    did the way the book says , ( seems to be in phase 120 ) , checked rod end play as per book, ,and checked bearings , guess i was very lucky , no major damage , 3 pistons and gasket set , again thanks to all your help here . Ski golf nut , did not see you or your daughter this weekend in Dallas town. Planning on rounds 7 and 8 ?
    Ps , I found the best tool to work on Pro 785 's , a bottle of number 7

  9. #9
    pro785project towman1987's Avatar
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    SLOAN, I just recently finished my pro top end rebuild.. It was my first rebuild and went pretty well.. I went with wsm 750s and US Chrome had to weld, grind and replate one cylinder for me(300 shipped). I found pistons and a COMETIC topend gasket kit for 315 shipped on AMAZON. everything went as well as it could with tripples, they are a huge PITA!!! but well worth the blood, sweat, tears and beers.. I have burned 25 gallons through it so far and thanks to beerdart, no adjustments needed on the carbs or anything!! Keep us updated with yours.

  10. #10
    skigolfnut's Avatar
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    My daughter went on Sunday to say her good buys to all her race friends, she joined the Navy and goes in in August, she will turn 18 in boot camp,


    I had a 13 USSSA baseball tournament with my son's team last weekend to pre pair for the world series, they won the state championship 2 weeks ago,
    hope to see everyone at rounds 7 and 8

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