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Discussion Starter #1
have a 500 xc 99, with burnt piston, what brand of repl should i look for oem or wiesco? can you buy just 1 oem? the fiche states 2.

now for the next question- what is the cause, is this something that happens to 2 strokes or is there a reason? should i look for a cause? the ring land is missing (you can see the ring from top veiw) this sled has approx 2k miles
thanks for any help
 

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Premium Member
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34,103 Posts
Which piston (mag or pto side)?
Usually it is the pto side that fails due to crank seal failure (lean condition).
Poo (fugi) engines tend to perform best with oem pistons.
 

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Discussion Starter #4
it is the mag side, i have it apart now, the piston looks like it broke instead of burnt. the cyl looks like it can be used over, top of piston and cyl head .is beat up from the parts. looking at the under side of piston looks new , no discolor
 

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If the piston skirt failed, you may want to replace both pistons to ensure the other one doesn't fail in the near future. Piston skirts usually fail from fatigue and excessive clearance between the piston and the cylinder wall.
 

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Breaker of Balls
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313 Posts
i hear that with wiseco pistons you need to warm up your sled longer to get the piston warm, cuz it cools fast? i dont know me and my friend were talking engines one day and we started talking about pistons he says he read somewhere that wiseco are built for racing, so if you shut your sled off for even a little bit you eed to warm it up again before you munch on the throttle.

i dont know if this is truthful or not, maybe just something to look in to.
 

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Discussion Starter #7
i think i found the problem, i think- the pistons ring gap is toward the exhaust port, that isn't correct is it?. my logic is gaps should be away from big opening.
where can i locate a SPI piston catalog?
 

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SD Rider
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4,337 Posts
Which piston (mag or pto side)?
Usually it is the pto side that fails due to crank seal failure (lean condition).
Poo (fugi) engines tend to perform best with oem pistons.
99 XC 500 had a Liberty didn't they? Either way, I've heard lots of mixed thoughts on wiseco. Some love them, some don't. I'd stick with the OEM-type pistons just because they're cheaper.
 
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