2015 piston issue

F_ast · Feb 20, 2019

So having some problems with my 2015. This sled has been a freight train since i got it. Much stronger than most imo.

But all of a sudden it took out 2 sets of plugs within a short period. Sled has 1600 miles.

Decided to pull top end after seeing some scoring on the pto side piston through the exhaust port. At first i figured i just cold seized it, but upon further inspection there is a single distinct score line in one place only. Approx 1/64" deep by eye, 2 chipped rings in line with the score line and a raised edge on the top edge of the piston.

Anyone seen this before? Im thinking power valve came in contact with the piston. Thoughts?

Trying to upload pics.

F_ast · Feb 20, 2019

Here are my pics

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kiliki · Feb 21, 2019

looks like a valve hit it to me. you can grind just a bit off the edges of the valves to prevent this. Look and the jug at the valve hole. the valve has a "stop" flat surface and some have had the stop wear into the jug letting the valve sink in too far.

sno*jet · Feb 21, 2019

its a common thing that I believe goes mostly unnoticed on cats. lots of threads on it if you google power valve hitting piston cat 800. hopefully the ctec improved the design.
I took the Dremel to my 17 before day one, and try to keep an eye on them, my pistons have marks last time I looked but not grooves yet.
I believe it goes unnoticed because it doesn't really get into the rings. sled still runs pretty good like that for years.

jim · Feb 21, 2019

Yep. That is from the powervalve. I had this happen to both pistons on my turbo. Caught it early though. I removed a decent amount of metal from the powervalve and even on a sensitive to the low end turbo, I did not notice any difference in how it ran. Can certainly turn into a big problem...so good catch.

Sledbrain2 · Feb 24, 2019

F_ast said:
So having some problems with my 2015. This sled has been a freight train since i got it. Much stronger than most imo.

But all of a sudden it took out 2 sets of plugs within a short period. Sled has 1600 miles.

Decided to pull top end after seeing some scoring on the pto side piston through the exhaust port. At first i figured i just cold seized it, but upon further inspection there is a single distinct score line in one place only. Approx 1/64" deep by eye, 2 chipped rings in line with the score line and a raised edge on the top edge of the piston.

Anyone seen this before? Im thinking power valve came in contact with the piston. Thoughts?

Trying to upload pics.

So I read your post the other day, heading to the mountains in a 9 days, we actually have snow here to ride a little, clean the clutches and take 2 m8000 for a test run, mine is a 14 with 1800 miles, I notice that its not pulling rpm like it should have 9000 weights and above at 1000 ft, normally jumps past 8200 with 3/4 throttle, I take my sons out his rips, pulls skis up, now I know something is wrong. It did flutter or make a different sound when I gave a burst of throttle for a sec going up a bank of snow. My question is did the motor sound different or make a noise? I have the sled parked in a storage in trailer, as luck would have it we got an actual blizzard last night so not sure if I can even get to it to pull the exhaust. I am guessing if this is the issue I will need a cylinder and pistons,

Sledbrain2 · Feb 24, 2019

sno*jet said:
its a common thing that I believe goes mostly unnoticed on cats. lots of threads on it if you google power valve hitting piston cat 800. hopefully the ctec improved the design.
I took the Dremel to my 17 before day one, and try to keep an eye on them, my pistons have marks last time I looked but not grooves yet.
I believe it goes unnoticed because it doesn't really get into the rings. sled still runs pretty good like that for years.

How much do you take off and is it just the corners? thanks

F_ast · Feb 24, 2019

Sledbrain2 said:
So I read your post the other day, heading to the mountains in a 9 days, we actually have snow here to ride a little, clean the clutches and take 2 m8000 for a test run, mine is a 14 with 1800 miles, I notice that its not pulling rpm like it should have 9000 weights and above at 1000 ft, normally jumps past 8200 with 3/4 throttle, I take my sons out his rips, pulls skis up, now I know something is wrong. It did flutter or make a different sound when I gave a burst of throttle for a sec going up a bank of snow. My question is did the motor sound different or make a noise? I have the sled parked in a storage in trailer, as luck would have it we got an actual blizzard last night so not sure if I can even get to it to pull the exhaust. I am guessing if this is the issue I will need a cylinder and pistons,

I decided to look at it because it started to take out plugs regularly. The thing still ran strong but it seemed to have a flutter or minor stumble past its regular cleanout after idle.

I will tell you though the sled is much stronger now after a fresh topend.

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Sledbrain2 · Feb 24, 2019

14 800

Do not think I have the issue,I did have one spark plug that was finger tight or less than finger tight, last year sled got seriously flooded on a cold morning ended up putting one or the only plug you can with pulling the hood, that is the one that was loose. Both cylinders have 138 lbs of compression. Here are a few pics, there is one score line but I think that is from carbon build up, Piston does not appear to be deformed or damage from valve.

F_ast · Feb 24, 2019

Sledbrain2 said:
Do not think I have the issue,I did have one spark plug that was finger tight or less than finger tight, last year sled got seriously flooded on a cold morning ended up putting one or the only plug you can with pulling the hood, that is the one that was loose. Both cylinders have 138 lbs of compression. Here are a few pics, there is one score line but I think that is from carbon build up, Piston does not appear to be deformed or damage from valve.

I'm not entirely sure what would cause a center score on the Piston like that. That's most likely from something going through the engine. Electrode of spark plug something coming in through the air Box Etc. But you have a serious amount of blow-by on those pistons. Typically caused from deformation or the Rings not seated two cylinders properly. If you look back at the pictures of my Pistons I have no discoloration below the Rings like on yours

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Sledbrain2 · Feb 24, 2019

every lay down motor I have had has the same blow by, 700, 1000, this 800 looks very similar to those, I have had a m7 that had carbon build up that scratched the side or face of the piston.

sno*jet · Feb 24, 2019

Sledbrain2 said:
How much do you take off and is it just the corners? thanks

much as you feel comfortable, I basically smoothed the edge all way across. upper edge, or whichever one comes closest (been too long foggy memory) I thought I saw a mark like it rests on piston and thought no way should it be doing that. maybe that was on the second go round. when it was new I just did the sides where everyone gets that dig in eventually. maybe using an extra gasket would help. im no expert, still kinda new to these. your pistons look good to me from that angle.

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2015 piston issue

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