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Discussion Starter · #1 ·
Alright, since we got snow last night i thought i would take my 2002 Z440 Sno Pro out for a ride. After i got about 2 miles the motor started sputtering so i slowed it down and shut it off. I took the spark plugs out and the one was white, the other was fine. So we pulled my sled home and i have taken the heads and cylinders off and well the one piston has a hole in it. My question is what could have caused that to happen and now do i just need to replace the piston and rings and hone my cylinders? The other piston is good and the heads are fine, the one cylinder has just a few tiny scratches in it, the other is fine. The motor doesn't even have 1000 miles on it also. Any suggestions would be helpful.

Thanks, Casey.
 

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too black never hurt nuttin, but that is deffinetly caused because that cylinder was burning WAY too hot. check and see if there is maybe a clog in the gas line, causing not as much gas to get in there, because it looks like that 1 cylinder is burning WAYYYYY too lean
 

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i just did some reading on that and i came up with pre-ignition. which is from being way to lean.

even without the hole in the piston, it still looks like somethin is up because it is too clean.
 

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i would go right to the carb on that side and very carefully disassemble it. try to remove the bowl without dumping its contents. if it has any water in it, that would be a prime reason. water wont atomize like gas, it will plug the jets and lean out that cylinder while the other side runs fine. also remove the jets and look for any obstructions. a small piece of grit will restrict fuel also. the top of the piston is almost free of carbon, and the detonation on the exhaust side are a lean burndown. disassemble both carbs..... could be a leaking crank seal too. :m2c: THIS IS JUST MY OPINION. take it for what its worth
 

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well you propably dont even needa hone the cylinder, are there any scuff marks, because your rings appear to be fine, its just the top of the piston. how does the head look? but ya, replace the piston and rings, hopefully the head is fine, if not then maybe someone can clean it up for you? a little pitting(smalldivits) in the head wont hurt nuttin, but you dont want ne chunks on it.
 

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i would go right to the carb on that side and very carefully disassemble it. try to remove the bowl without dumping its contents. if it has any water in it, that would be a prime reason. water wont atomize like gas, it will plug the jets and lean out that cylinder while the other side runs fine. also remove the jets and look for any obstructions. a small piece of grit will restrict fuel also. the top of the piston is almost free of carbon, and the detonation on the exhaust side are a lean burndown. disassemble both carbs..... could be a leaking crank seal too. :m2c: THIS IS JUST MY OPINION. take it for what its worth[/b]

Yes, Exactly as Barncat has said. You have, had a dirty carb causing a lean condition. The other thing that could have happened is an air leak. Could be crank or carbs. Had a sled once with a leak in the carb causing a lean condition. Get the cylinders honed and new wrist pins, clips, pistons w/ rings, install with new gaskets and you'll be good as new. Well that is after you clean the carbs. What kind of summerization did you do in the spring?
 

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Discussion Starter · #16 ·
I had the tank empty at the beginning of the summer, about july i had to move it so i just threw some in, that must be the problem. I never thought to check, just filled the tank a couple days ago and topped off the oil and went, couple miles later here i sit while my friends ride.
 

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Discussion Starter · #18 ·
Yeah, i bet its just the carb but gosh this blows, my 99 zr 500 efi blew up 2 years ago, then it blew up again not even after 500 miles went past on the speedo the year after, i seem to have some pretty rotten luck with these sleds.
 

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I have had a few pistons that looked like that in my day. Most were from either water in the gas or a dirty carb. Another problem I had on my 99 ZR700 was a slightly sheared flywheel key causing pre ing. I went through 3 sets of pistons before I figured that one out. Might be worth checking and is easy to do.
 
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