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  1. #1
    kmaher's Avatar
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    Stumped on how this can happen....?

    Maybe some of the gurus on here have seen a failure like this before and can tell me how this can happen, but I am sitting here stupified wondering how this ensued...

    I just rebuilt the top end on my 1300r about 5 hours ago because of slightly lower compression on cylinder 3. Turned out the rings were worn and I had a loose locating pin, so I decided to refresh the entire motor. Rebuild went as expected (other than the wrong piston rings being shipped with my Pro-X pistons, but that was resolved).

    Anyway, I went through a nice and gentle break-in period, and all was going as planned. Compression was starting to bump up a little bit after every time out...went through a tank and a half mixed at 30:1, and then reverted to the traditional 40:1 last time I went out. Was looking forward to finally being able to give it some throttle...

    Anyway, the test run went very well until I came back to dock, when it stalled. Cranked it over and it started right back up, but I heard a "pinging" sound. Got it back on the trailer, took it home, and checked compression after it cooled. Compression continued to improve in cylinders 1 and 2, but cylinder 3 was down. WAY down. I knew I had a problem, so I pulled the head.

    Anyway, this is where I get stumped. Top of cylinder head showed signs of shrapenel bouncing around between the top of the piston and the cylinder head. Beautiful scoring marks on the side of the cylinder and piston (This is not a PV motor, by the way). So I naturally need to determine what the culprit was, and it turned out I was missing one of the washers between the needle bearing and piston.

    Anyway, how would this washer make its way out? It's over the wrist pin, so my only thought would be heat expansion would cause the washer to explode, but that seems far fetched. Then, let's pretend that DID happen....I would think it would end up doing a dance in the bottom end, wreaking massive havoc. My bottom end is untouched. SOMEHOW after the washer mysteriously found its way off the wrist pin, it made its way up the side of the clylinder and on top of it, where it bounced around for a while, making sure to ruin a perfectly good cylinder head, and bits of the washer are lodged in both the piston and head.

    Has this happened to anyone else before, and more so - HOW does this happen? I'm not complaining that my bottom end got away unscathed, but that's where I would have expected it to end up.


  2. #2
    Wrench's Avatar
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    My guess, you dropped one of the washers down in the crank case when putting the piston on. Once you finally opened the engine up, there was enough up draft to suck the washer off the bottom of the crank case. Or just the fast rotating crank threw the washer up under the piston.


  3. #3
    Dave in DE's Avatar
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    I agree with wrench on this one. No way possible to come off wrist pin. Had to of been dropped and not noticed.

  4. #4
    kmaher's Avatar
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    As much as I hate to admit it, and I swear I checked and double checked as I was reassembling, this is the most likely culprit since the washers are installed blindly and take a contortionist to get in there.

    I could complain about it, but I should really just consider myself extremely lucky for it somehow not causing damage to the bottom end.

    Oh well, now the search for a reasonable head begins. Everything out there is trashed.....

  5. #5
    Tool Bag water worx's Avatar
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    Thats one reason I dont use washers.....never had a issue because of not using them.

  6. #6
    kmaher's Avatar
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    Quote Originally Posted by water worx View Post
    Thats one reason I dont use washers.....never had a issue because of not using them.
    I was wondering about the necessity of them myself. It's not like the needle bearing would have a ton of room to move around without the washers.

    Now I need to decide if it's worth it to rebuild this top end or make this a conversion ski. I've had the bug for a while, but didn't want to incur the cost. Now, with the price of a head (assuming I can even find on in good shape), a piston, and having the cylinder sent out to Millennium for a replate, I'm well over a grand. If I part out the motor, I can probably make $2k, which gets me a decent way to purchasing a salvage SHO machine, which I bet I could get under $4k.

  7. #7
    Tool Bag water worx's Avatar
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    Dont get to optimistic on your "salvage" jet ski parts.

    Everybody & their brother is selling used jetski parts & the prices are low.

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