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Discussion Starter · #1 ·
We went down a slope with minimum throttle now and then when my buddys summit 800 X 04 made a clanking noise and engine stopped.
we didnt try to start it again. crank turns half with compression from piston then half turn crank is without resistance as if one piston let go. also engine seem to be loose rocking back and forth. still holding all coolant.
Rings were recently replaced with Cudneys. Engine ripped until now.

We towed it to the shoreline to bring it back by boat one of these days.

Any ideas what we might be expecting?

Thanks for comments
 

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Discussion Starter · #2 ·
we took it apart. piston ring on clutch side is chewed up with some of the piston. ring gap seem to have travelled ccw until perhaps the gap or pin got caught in the exhaust port.

is it possible to slide the cylinder on piston if the ring gap is not directly on the pin?
or could the pin fall out to cause the ring to rotate anyway?

thanks for comments
 

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If your pistons are the only thing screwed up your lucky!!! I'd also look on the inside of your head for carnage.

Piston rings should not rotate around on the piston. I'd replace them. And since your already there, replace them with Kelseys RK TEK top end. That'll send ya out of the shop wide eyed!!!


Remember, use a fresh base gasket (probably 6 holer). Look for debris down in your crank casing also.

Good luck on the fix!
 

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Mohabba said:
heres the "good" piston
why am i concerned about this?
[snapback]742990[/snapback]​
Looks like your in the market for a new cylinder. Have to hate how those pin wear out like they do.
 

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I have seen the same problem on three 800 ho motors.
The motor is detonating from bad gas or wrong grade of gas or jetted to lean.
The motor pings until the ring pin is pounded into the piston, the ring is then free to spin until the ring gap finds the exhaust port. The ring then hits the rave valve or the exhaust port and breaks off a piece of the ring and piston. If you are lucky the ring only breaks off a small part of the piston and the pieces exit the exhaust. If you are unlucky the broken pieces stay in the cylinder and it takes out the head, cylinder and piston.
 

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skidoox said:
I have seen the same problem on three 800 ho motors.
The motor is detonating from bad gas or wrong grade of gas or jetted to lean.
The motor pings until the ring pin is pounded into the piston, the ring is then free to spin until the ring gap finds the exhaust port. The ring then hits the rave valve or the exhaust port and breaks off a piece of the ring and piston. If you are lucky the ring only breaks off a small part of the piston and the pieces exit the exhaust. If you are unlucky the broken pieces stay in the cylinder and it takes out the head, cylinder and piston.
[snapback]743477[/snapback]​
Yeah, seen that a couple of times on mine and a friends sled. Great motors aren't they
 

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same thing happen to me, on a 800 2004 and my old 2005. twice time its happen when engine is cold. I expect that aluminum piston make more expension than the steel ring pin, and the pin come to be slack in the piston. Now I heat correctly my engine before run wot.
 

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It could have happend on the way up the slope, going WOT most likely!

Going up it pounded the pin in or out then the ring started spinning and finally found a port while you were going down the hill.

Either way that sucks and i hope it doesnt cost a small fortune to repair.
 
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