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  1. #1

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    787 bottom end question?

    Iam doing a top end on a gtx, took it apart one piston is shot, grey lines main suspect, filter clogged. anyway checking the bottom end and iam not sure how soft its supposed to turn. there is no play at all on the crank shaft no devrey from piston in the bottom end, I turn it by hand and its not soft all the way around is it supposed to be like that? doesn't seem like its touching anything. but iam not sure.


  2. #2
    wkuadam07's Avatar
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    Is the engine out of the ski? If it's still in the hull then you are probably feeling the impeller drag the wear ring on one side.
    Is the rotary valve cover and rotary valve removed? It should be totally free and smooth all of the way around with no pistons attached...

  3. #3

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    engine is out rotary valve and cover are on..no pistons attached. you can turn it by hand but I feel its not completely free

  4. #4
    canuck's Avatar
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    Since the engine is out you might as well split the cases and have a good look at the crank and counterbalancer bearings to see what is binding.

  5. #5

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    honestly didn't want to split the cases but I guess ill have to now...

  6. #6
    surferd15's Avatar
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    It should be smooth all the way around. Take the rv cover off and see if it smooths out. But before you do that, put the engine at top dead center, carefully pull the rv cover off and make sure the rv disc (forget the name) stays in place so you can mark the timing. Is the head chewed or piston broken?

  7. #7

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    piston messed up on top, head chewed, bottom end looks clean no devry from piston. any marks to put on tdc, I have top end off.

  8. #8
    ncdoo's Avatar
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    No marks needed.
    Quote Originally Posted by Alex3012red View Post
    piston messed up on top, head chewed, bottom end looks clean no devry from piston. any marks to put on tdc, I have top end off.

  9. #9
    wkuadam07's Avatar
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    I never mark the timing... I bought a degree wheel so i can set it properly.

  10. #10

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    took off the rotary valve, and that was it, it was rubbing on the walls, ordered a new one, and I have a cover from a previous engine, i'll use the better one of the 2, the timing seems to be very easy to do, I looked at the manual and a couple of videos on youtube, and it should be easy even though I did mark it.. if its at tdc the rv should be fully open at mag side and the other should line up at 146.5 deg.

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