951 melted piston
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  1. #1
    Frequent Poster
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    951 melted piston

    Decided to pull my raves out of my 951 after noticing a couple hundred rpm loss at WOT. Looked down the hole and seen that the piston is melted above the top ring. Looks like a 45 bevel that matches the exhaust port. Was on PTO cylinder. Can't see any other damage. Stock tune. Lots of piston wash and darker plugs. Anyone else ever run into something like that?

  2. #2
    Top Dog Hydro-Mike's Avatar
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    Re: 951 melted piston

    Quote Originally Posted by Jet Cowboy View Post
    Decided to pull my raves out of my 951 after noticing a couple hundred rpm loss at WOT. Looked down the hole and seen that the piston is melted above the top ring. Looks like a 45 bevel that matches the exhaust port. Was on PTO cylinder. Can't see any other damage. Stock tune. Lots of piston wash and darker plugs. Anyone else ever run into something like that?
    Next you need to pull the head and post a couple pictures. seeing the top of the pistons and the conditions of the piston sleeve wall will help. The picture of the sleeve wall above the exhaust port.
    Last edited by Hydro-Mike; 09-13-2020 at 09:24 PM.

  3. #3
    Top Dog SURFnTURF's Avatar
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    Re: 951 melted piston

    If its melted on the edge like you say more than likely its an exhaust manifold/flange leaking gasket or maybe a head gasket and water (steam) is being super heated as its being forced over the edge of the piston due to the transfer of exhaust gases through the chamber and exhaust port
    I once had a cylinder liner leak between the cylinder casting and top deck of the cylinder,it started to rust behind the liner and pushed it out of shape even after two rebores.
    But water ingestion is your problem

  4. #4
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    Re: 951 melted piston

    Interesting. I have seen others suggest the water leak on the internet. I have never seen something that. Has good compression. No stuck rings or galling on the skirt. I will post some pictures early next spring if I tear it down. Was wanting to spend some money on my rx p not this thing. May just sell it. I am going to have a hard time not hop'n it up if I go in there. Fun ski for sure.

    Seems to be somewhat common for the pto on both the 787 and 951. Even seen some holes lower down on the skirt. The pictures generally seem to have more signs of a lean condition or detonation.

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