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Discussion Starter · #1 ·
Hello does anyone know what could have possibly happened to this motor. The ring caught the exhaust port on both pistons which I thought was weird. Ring then gouged the cylinder above the exhaust port. Sled was warm then sat for half an hour then I started it jumped on it let it warm up for like a mile until coolant temp was 125f then hit throttle and quit pulled it apart and saw this. We were thinking that it possibly cold seized because it happened to both pistons but unsure. What does everyone else think.
 

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Hello does anyone know what could have possibly happened to this motor. The ring caught the exhaust port on both pistons which I thought was weird. Ring then gouged the cylinder above the exhaust port. Sled was warm then sat for half an hour then I started it jumped on it let it warm up for like a mile until coolant temp was 125f then hit throttle and quit pulled it apart and saw this. We were thinking that it possibly cold seized because it happened to both pistons but unsure. What does everyone else think.
lean burn down, no wash
 

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X2 lean burn.
 

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Discussion Starter · #4 ·
But I had egts on and they never went above 1200 and according to plug readings thats still ok. It sat for a couple days before this pic also could that effect wash
 

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Discussion Starter · #7 ·
Yep locator pins are still in but top one is pushed in now but that may of happend when ring caught exhaust. Also these are weisco pistons.
 

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Bad gas? I just took out my turbo pistons. Looked almost just like yours but with more of a melt down. Egt and afr both read in the safe zone..
 

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Discussion Starter · #10 ·
I dont really think its bad gas either cause we buy are gas in bulk and have it at home and i put over 500 km using this gas and another skidoo a zr 440 is also still using this gas and have had no trouble. If there was a coolant leak would it show up on the plugs because right after it blew up the plugs looked normal. Although a wee little amount of snow dropped into gas tank when i was fueling like not even a teaspoon. I put fuel stufff in there right after this that is supposed to absorb water but this was like 100km before it blew. So I Don't Know my dads theory is that when I stopped the cylinder cooled and contracted but the pistons didnt then when i started it again the rings stuck.
 

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Crowns of pistons show signs of detonation. Side and edge of piston are melted. Ring locaters are pushed in by detonation as well.

You have only so many variable that will cause this: Lean mixture, bad gas, too high compression, advanced ignition timing, using ES suffix plug instead of ECS, posible water in float bowl. Most likely a combinatio of any of the above.
 

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Discussion Starter · #12 ·
It doesn't look like this piston had any detonation damage though this was the mag piston and the other piston doesn't look as melted as it does in the picture, in person it looks like the ring pushed up and broke that chunk out of piston and then just melted were it was broken there and nowhere else. I Don't Know what do you guys think now?
 

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Discussion Starter · #15 ·
They must be machined alluminum because they are not ceramic I dont think. They were regular m series weisco.
 

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Check your rave clearance to piston ring. Mine were just touching the stock rings and the carbon on them was getting cleaned off in the centre of them. I took .015 off the top curve to be sure, which doesn't affect the height of it. That's a large port, and the ring does bow out into the port under heat and pressure. If there isn't enough chamfer on the top radius the ring can get slammed back into the groove accelerating the wear on the ring lands. Just a few things to check when assembling. And if your going to use wiseco pistons, for sure lose the thermostat, and do the long warmup thing until the rear exchanger is hot. A billet head keeps the coolant temp lower and more consistent too.
 

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They must be machined alluminum because they are not ceramic I dont think. They were regular m series weisco.
I only ask because a ceramic coated top is a dull rougher finish and the wash will look a little different, it will not be a shiny washed off area like a non coated top. As Ebob stated those were lean, no wash evident. Underside of piston crowns will show the heat.
 

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That piston top looks way to lean. When we see them that lean (clean top) many times the crank bearings are also shot.

Good call on the Rave valve clearance.
 
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