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Discussion Starter · #1 ·
98 zl440
3800 miles, all stock
went riding today, about 30 degrees, I was breaking trail for about 10 miles then all of a sudden a major power loss. Got it home and found this? Lean, lube, lack of coolant? Before i put any money into this I want to figure out what caused this. The hole is on the exhaust side. Took out the cylinder as well. No damage to any other part of the piston

[attachment=64944:picture_0827.JPG]
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I think you answered your own question for the most part. "I was breaking trails for about 10 miles". These two strokes simply don't like a heavy load for long periods of time. Some of them won't last a full throttle blast across a lake. Too many rpm's, too much heat, not enough time to recover and cool back down. Seems like liquid cooled sleds will burn down even quicker then a fan cooled even though you would think not. Breaking trail on a sled can be brutal. Like hooking a 3 bottom plow on the back of a pickup. It would not last long doing it. You may have got some bad gas but I think the trail busting simply overheated it and burned it up. Later.
 

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Discussion Starter · #3 ·
<div class='quotetop'>QUOTE (MIDMICHIGAN440 @ Mar 1 2007, 07:33 PM) <{POST_SNAPBACK}></div>
I think you answered your own question for the most part. "I was breaking trails for about 10 miles". These two strokes simply don't like a heavy load for long periods of time. Some of them won't last a full throttle blast across a lake. Too many rpm's, too much heat, not enough time to recover and cool back down. Seems like liquid cooled sleds will burn down even quicker then a fan cooled even though you would think not. Breaking trail on a sled can be brutal. Like hooking a 3 bottom plow on the back of a pickup. It would not last long doing it. You may have got some bad gas but I think the trail busting simply overheated it and burned it up. Later.[/b]

I was kind of thinking the same thing, I put 30 miles on the sled before this happened. Anyone else?
 

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hmm, you shouldnt have catastrophic failure like that just from a burn down. Because the top of the piston is completely gouged up, you had some sort of debris in there. Take a closer look at the ring retaining pin, because it looks a lot like that pulled out, ring ends rotated around to exhaust port and WHAM, hooks the ring and yanks a chuck of ring off with some piston to go with it. That would be my guess, but your pictures are a bit unclear to tell
 

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Discussion Starter · #5 ·
<div class='quotetop'>QUOTE (ArcticRedNeck @ Mar 1 2007, 11:48 PM) <{POST_SNAPBACK}></div>
hmm, you shouldnt have catastrophic failure like that just from a burn down. Because the top of the piston is completely gouged up, you had some sort of debris in there. Take a closer look at the ring retaining pin, because it looks a lot like that pulled out, ring ends rotated around to exhaust port and WHAM, hooks the ring and yanks a chuck of ring off with some piston to go with it. That would be my guess, but your pictures are a bit unclear to tell[/b]
Sorry about the bad pictures. The one ring looks as if it comes together right over the exhaust port, I thought this looked weird, so maybe it did move. If this is the case, is it something I did? Or is simply old age or manufacturer defect the only cause of the retaining pin coming out?

Another question
Do I have to worry about chunks of piston in the crank area or because this occured on the exhaust side it all blew out? There are no score marks below the hole, meaning I don't think any chunks went below the piston.
 

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yes you do have to worry about the crank. I had a sled that I had blow up many times. dealer never ripped down completly. final got new bottom end no problem from then on. Any alluminum in a bearing will blow it again.
I hate when that happens.
jd
 

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I aggree looks like debris from something caused damage. Possibly C clip fell out of piston groove or needle wrist pin bearing on piston failed and seperated. You won't know for sure until you remove pistons. Also check connecting rod bearings. You definatly should split case and wash all parts in solvent to make sure there are no metal filings or grit in anything.
 

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Discussion Starter · #8 ·
Ok, here's the scoop
Appears the top piston ring caught the exhaust port, broke half of the ring off, (that is what caused the debris). I'm guessing after that it started running lean and burnt a hole in the piston. Plugs didn't look that bad. Went to the local snowmobile salvage yesterday at 10am right when the doors open, bought a completely remanufactured cylinder, piston, and gaskets for $350 eekkk, got home at noon, installed everything and was back on the trail at 5pm. Sled ran great for all 100 miles I put on it. Looks like I should do the other piston as preventative this summer. Guy at the sled shop said that having the rings catch the ports is not all that uncommon for this generation of cats???????????
 

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<div class='quotetop'>QUOTE (mopar4u @ Mar 3 2007, 12:40 PM) <{POST_SNAPBACK}></div>
Ok, here's the scoop
Appears the top piston ring caught the exhaust port, broke half of the ring off, (that is what caused the debris). I'm guessing after that it started running lean and burnt a hole in the piston. Plugs didn't look that bad. Went to the local snowmobile salvage yesterday at 10am right when the doors open, bought a completely remanufactured cylinder, piston, and gaskets for $350 eekkk, got home at noon, installed everything and was back on the trail at 5pm. Sled ran great for all 100 miles I put on it. Looks like I should do the other piston as preventative this summer. Guy at the sled shop said that having the rings catch the ports is not all that uncommon for this generation of cats???????????[/b]
just because you hade no problem in a 100 miles don't mean you won't have more problems later. you better split the cases and take out all crap that got in air box also. trust me there is metal hiding in there somewhere.
 
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