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  1. #1

    PTO Piston Failed - Top End or new engine?

    Well, it happened. WOT, then some noise, then a loss of power. My 99 SLTH died.

    When I inspected the PTO piston I thought it was only cracked. However, after pulling the piston I discovered most of the lower half of the piston was missing big chunks. There was metal debris and small chunks in an area to the left and right of the connecting rod. I think there are holes in this area to allow oil to pass back to the crank. However the holes were plugged with piston debris.

    The MAG piston and rings looked ok.

    Prior to failure the compression was 100 PTO and 110 MAG. I had been dealing with a bog/die while trying to accelerate above idle. I traced the bog/die to a hole in my fuel cap.

    The ski was running great after I fixed the fuel cap. You know what they say "it runs best just before it fails"

    I am worried about all the debris that went into the crank area. I think I should go for an engine instead of a top end.

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  2. #2
    la90043's Avatar
    Join Date
    Oct 2006
    Los Angeles
    well at least you'll need to open the case and clean it out of debri

  3. #3
    Click avatar for tech links/info K447's Avatar
    Join Date
    Jul 2007
    near Toronto, Canada
    Quote Originally Posted by tjruberg View Post
    ... I am worried about all the debris that went into the crank area. I think I should go for an engine instead of a top end...
    If you pull the engine apart, you can inspect the bottom end and crank shaft, and clean all the debris out.

    If the bearings look, measure and feel good, and you are feeling lucky, you can put it back together with a refreshed top end and new crank seals.

    If you really want to be sure, you can have the crank rebuilt with new bearings. Not too expensive for a twin.

  4. #4

    Join Date
    Aug 2006
    Bearings on the PTO side will be garbage. they might look ok, but they won't last long at all.

    It's time to go through the entire engine. Look at you other pistons, i'm willing to bet you may have more cracked skirts of the other pistons.

    EDIT: the last two 1050's I've torn apart ended up being 1200's! Brand new 1200 cranks for $600, a little bore and port, and you'll be happy!

  5. #5
    Pulled the engine, found lots of piston chunks in the PTO reed valve area. I recently installed Carbon Tech Reeds but there was no metal there when I installed them.

    Red, yeah, no way I will trust the crank now. Been there done that.

    One section of the failed piston had an area that was cracked but smooth, like it had been there for a while.

    Anyone know how much for a an engine rebuild? crank, cyl, boring, pistons, gaskets..............

    It sure was a fun ski, I'll rebuild or by a rebuild.

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