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Trail monkey

piston skirt broke...why , kx60 , 1 year on it

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what would be the cause of a piston breaking at the skirt line, piston only had one season on it, in my boys KX60

Thanks

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You asked a lot from a piston to go a whole year w/o changing and that's why it broke. When my son ran his 60, we did the top end no less than 4 x's a season. :ride:

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My friends KDX220 broke the skirts off the piston almost a year ago. They determined that the bottom end bearings got ground up which allowed the piston to vibrate side to side in the cylinder. They had to replace like everything in that motor.

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My friends KDX220 broke the skirts off the piston almost a year ago. They determined that the bottom end bearings got ground up which allowed the piston to vibrate side to side in the cylinder. They had to replace like everything in that motor.

exactly. i have seen this happen in 85's many times. trail monkey, i would replace the bottom end bearing also. i have seen many times where they just replace the top end and when its all put together the bottom end bearing explodes and peices of the bearing get on top of the piston and screws everything up.

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The stock one is cheasy/thin. :ride: Compare a Wiseco to the stock one. Much thicker. :ride: Plus, think of the torture that little piece of aluminum goes thru-hot cold, wot, idle, shaking side to side as it goes thru a stroke. Actually amazing they live that long at all. Our kx60 made it 1 and 1/2 seasons, finally gave up when my youngest :ride: decided to prove that water cannot be compressed-over the seat deep!

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Don't know if it is still the same, but when I bought my youngest son his KX-60, the owners manual emphasized that the rings should be replaced every three races and the piston replaced every six races. Even if your son doesn't race it, the piston still takes a beating. Piston, rings, and bearings are cheap insurance for what it's probably going to cost you after the skirt broke off.

Cheers,

Mac

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High Rev = High Pressure = High wear

Basically that is WAY too many "high's" to go a whole year.

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i've also heard that pistons can "crystalize" if you start the engine and shut it back off without letting the engine warm up. The sudden heat cycling will make the piston brittle. dont know if its true, but hey, you never know.

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If there is any extra bearing clearance, the piston will travel further down in the bore and hit the crank and break the skirts off, especially under load (powerband).

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