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  1. #31
    So three hours on new pistons and rings and I have this... This is exactly why I just replaced the pistons. Almost identical. Any chance I could save the head?

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    This is the #2 piston... okay?

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    Last edited by jhawker23; 08-19-2017 at 02:54 AM.

  2. #32
    And is this due to just being a bad gasket? It's peeling away. Aside from the bad piston, compression was still only 90/85 (cold engine) on the other two.

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    This was a WSM kit. Anyone know about their warranties and if they may replace the piston and rings?

  3. #33
    Yamaha artisan Cutlass's Avatar
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    It does not look like warranty. It looks like debris from a previous failure found its way into the combustion chamber and that's on you for not cleaning it up.
    Number 2 piston looks usable, maybe. The skirt coating looks pretty scuffed up, but maybe it's supposed to be that way.

  4. #34
    Could the head be re-used after smoothing out the burs? I'm taking the cylinders to a shop and hope it can just be honed.

    As far as debris, I don't know where it could've been hiding. I used a minivac attachment to get down into the case and also used shop towels to wipe out every place I could. Are there common hiding places? The other thing I'm worried about is why the compression on the other 2 cylinders were only 90.

  5. #35
    Yamaha artisan Cutlass's Avatar
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    Your elevation probably knocks down the compression a bit. Not sure how much. Maybe 10-15 psi ? So say, you should see 105 at your elevation...now where did the other 15 psi go? Ring sealing, gauge accuracy, larger then normal combustion chamber (i.e. Thick head gasket, thick base gasket, piston to head clearance too large for other reasons)

  6. #36
    So it's screwed. Took it to the shop and there's too much damage to the cylinder to hone. You can see where the ring was catching on the exhaust port. They estimated $900 to send off and repair as it's a monoblock.

    Sounds like I need to find a shop that could see if they could be bored out. Is replacing the sleeves a better option? I could either resleeve it to standard and keep the 2 pistons or possibly have it bored and replace 3 pistons (the 2 good pistons only have 3 hours on them).
    Last edited by jhawker23; 08-19-2017 at 05:56 PM.


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