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  1. #1

    Freedom 700 melted piston

    I have a 2004 Freedom 700 that I bought as a project. The heads were off and mag end piston melted around the edge. The PTO end piston was good. It looks to me like detonation but why on only one piston? This has one carb so a lean condition due to fuel should be evident on both pistons. Could I have air leaking at mag end seal? Any suggestions? I already have the cylinders bored and 2 mm over pistons but want to be sure of the rout cause before I put it together. I noticed the damaged head had been ground around the fire ring seating area from a previous failure. Could that cause the detonation?
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  2. #2
    could if be FOD instead of detonation? how do the reed valves look?

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  4. #3
    What is FOD? Reeds are good


  5. #4
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    That's mostly debris damage. Then somebody knew it wasn't running right but kept trying to ride it anyway. There's a couple ways this can happen. There could have been a water leak at a head o'ring....that will wash out the fuel and cause detonation....which eats away at the edges of the piston until a ringland is exposed....then the top ring snaps and the piece gets hammered into the head repeatedly. OR...that same scenario can happen from a plugged carb....then the lean mixture burns the edge of the piston away. OR....a lower end bearing starts coming apart and spitting metal....the bits get puked up through the ports and on top of the piston.....where they just keep getting hammered into the head until enough bits get puked that the crank finally locks up.

  6. #5
    Quote Originally Posted by Mel Nichols View Post
    What is FOD? Reeds are good
    Foreign Object Damage

  7. #6
    After a closer look at the head I realized it had been ground off (not planed) and is .010 thinner than the good head from the other cylinder. I’m thinking the higher comp ratio started the detonation and it went from there. The crank and big end rod bearing is good but the rod small end is damaged, likely from the melted piston. I’ve ordered a head.

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