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Discussion Starter · #1 ·
Starting yesterday, we went out on the lake for a little while, came back to do some clutch changes. The sled sat outside in the snow storm for a couple of hours. Moved it inside warm shop for the night.

Today, it started and ran great, as it usually does. Went out on the lake again, messing around.

I was going across the lake approx. 60-70 mph and it just quit like the kill switch was hit. Went to pull it over and it was locked up. Waited for a minute and pulled right over, started, but wouldn't idle. Pulled the plugs, found two were a nice cardboard brown and the third had aluminum all over it. SH!T!!!!!

Poured some oil down that cylinder, left the plug out and limped it home, while being pulled.

Here's the exhaust side:
20101212231018923_24996.jpg
Intake side:
20101212231049110_24996.jpg
Piston top:
20101212231121470_24996.jpg
Head:
2010121223121704_24996.jpg
Spark plug:
20101212231210814_24996.jpg


Air box was pretty dry (no snow or water in it), have the pre-filter on. Carbs had water drops inside of them. Crank seals only have about 2000 miles on them and look to be fine. I usually put a little fuel drier in the tank (red bottle), but forgot to this time. Cylinder looks good yet, just hone and it'll be good, no real scratches in it.

Could I have gotten water in the fuel and it froze in the jet on that cylinder?
Any other thoughts on how this could have happened?

Sorry a little long, just wanted to have every detail.
 

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How much fuel was in your tank when you brought it inside?

Bringing any vehicle from cold temperatures to warm will cause condensation in the tank. That is why you must used gas line anti-freeze in your tank.

Possible that water in your carbs could have doe that. Not positive, but you did say there was water in the carb, so water in the tank is likely too.
 

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Discussion Starter · #3 ·
Had about 3/4 tank of gas. I thought about condensation too, but remembered a bunch of people on here say they never have any problems keeping their sleds in a warm shop. Maybe they use a gas drier??
 

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If you run eth fuel, they say you should not add any HEET. I know I do, but a couple ounces to a full tank only.
 

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COLD SEIZE!!!
 

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That's not a lean burn.

Either cold seize, or possibly snow/water ingestion stripping away the lubricant. The crown of the piston looks good but I don't see any wash? Either the piston is pretty new or water steamed the carbon off the top.
 

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Discussion Starter · #9 ·
ripperd said:
That's not a lean burn.

Either cold seize, or possibly snow/water ingestion stripping away the lubricant. The crown of the piston looks good but I don't see any wash? Either the piston is pretty new or water steamed the carbon off the top.
I was running in 8-14 inches of powder when it happened. Didn't find any snow in the airbox, just a couple drops of water. Pre-filter was clean too.


whitexc said:
Is some of the crown gone? Almost looks that way in the pic.
Yes, it started to burn it away, it's almost 1/8" deep. Hard to get in pictures.



MX86 said:
proper piston for the bore you had? I'd check the other 2. and Like dean said, nothing for wash
Rebuilt the motor 2 seasons ago, have about 2000 miles on it. Other two look really nice.



I did find water drops in all the carbs.

What causes cold seize? Just wondering if there's a way to prevent it.
 

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I agree with cold seize. If you were lean the exhaust port side of the piston would most likely be slightly burned off on the top and the crown would be full of black carbon.
 

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The piston started to burn through, and there's aluminum on the plug from detonation.

There was water in the tank, and it wasn't froze because of being in the warm garage. And when it got sucked through the jet, it got froze by the cold air passing through the carb.

The jet started to clog and it leaned out

And there was water in the carbs when he got it home.
 

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Dude, am I missing something? Because I dont see any signs of detonation. The aluminum came from the piston and cylinder wall. Its not a lean condition. Check your oiler. Another possibility is a clogged needle and seat flooding and washing the cylinder.
 

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So with all that said, were you guys thinking water/snow ingestion? Water in gas?
 

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Ugly_old_Poo_kid said:
The piston started to burn through, and there's aluminum on the plug from detonation.

There was water in the tank, and it wasn't froze because of being in the warm garage. And when it got sucked through the jet, it got froze by the cold air passing through the carb.

The jet started to clog and it leaned out

And there was water in the carbs when he got it home.
+1 had this exact samething happen to me before, but I caught it before anything bad happened. If you had pulled the cap off the carb as soon as it happened I bet you would have seen ice buildup around the jet needle and near the pilot circuit outlet.

Got to be detonation right? If it was strictly from being lean then the exhaust side would be burnt up too, and the crown of that piston is messed up pretty bad.

Maybe it leaned out a little from the ice buildup, then the detonation did the real damage while the piston was a little hotter than normal? Lean condition and detonation working together hand in hand to kill your motor.

Sux bro, hope you get her back together soon. Good luck[thumb]
 

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the top of the piston is from detonation.
the sides are from lack of lube beings that there is 2k miles on the engine it cant be from a wrong fit.
lack of lube can be water or lack of oil.
 

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Discussion Starter · #17 ·
Well guys, I really appreciate all the input. I think I found another reason it burned. I split the case (might as well replace crank seals if doing a top end, right?) and found the pto side seal was a little melted.
I'm glad I ordered a full gasket set.[:)]
I still think there was an icing problem in the carbs too. There was more than a couple of drops in them, so that had to be an influence too.

Do you think if the carb iced up and leaned it out, it got that seal hot enough to soften up some?


Edit: Forgot to add: The oil on the pto side bearings was discolored. Bearings are fine though, still really smooth.
 

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i dont see lean damage. i see detonation from high engine temp or bad gas, water in the gas can make it bad.
 

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While you have the engine that far apart, spend the $$ and replace that bearing..
 

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This is what a lean burndown +detonation looks like :p
http://www.ripperd.com/gallery/images//Snowmobiling/08-09/kablooey/IMG_2258.jpg

That was only like an 8 second WOT pull too. Don't run too lean and try to race someone when your watertemp is a bit on the hot side! Yes, the cylinder needed to be re-nic'ed.
 
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