Need Motor Advise on an '08 800

[otterby]

So I'm debating weather to tear into this myself or shell out the cash to let the dealer figure it out.

While riding this morning we made it about 5 miles what the motor suddenly started bogging down and then just quit. Pulled a few times but it wasn't starting. I pulled over hard. Held the throttle wide open and it fired up. After about a minute it bogged down and quit again. The plugs were brown and dry. After doing this a few times it came to the point where the pull cord wouldn't budge. I turned the primary by hand and it felt fine then the pull cord freed up and we could get it started again. Eventually it started running rough after we started it so I towed it the rest of the way back. I can still start it but it sounds bad. If I give it some throttle it seems to come out of it but dies when I let off. The plugs are black now and sort of wet. Just curious if anyone has any ideas where I should begin looking. Thanks in advance

 

[otterby]

Update

So I started by checking the compression and it wasn't good. 110 on the pto side and 40 on the mag side. I pulled the head off and the pistons looked good but the mag side had some light scoring. Next I pulled the covers off the power valves and the mag side had a large chunk of ice in it holding the valve in the extended position. I then pulled the cylinders off and saw the extent of the problem. The mag piston was toast. The sides of the piston were completely ground up to the point where the rings were seized. The bottom part of the mag side cylinder is pretty chewed up also.

Does it make sense that the power valve getting stuck caused so much backpressure and blowby that within 5 miles of riding it completely wore down the side of a piston?

 

[volcano buster]

I'm no motor expert so I'm not going to post any magic solutions.

It appears that you need to relocate the airbox drain hole that is in the bottom edge of the airbox in the hood. The hood accumulates water and it settles down through this hole and drops exactly over the hole in the center of the exhaust valve housing. Don't ask me how the Polaris engineers screwed this up, but they lined it up perfectly. I'm guessing that is the cause of the water in the bellows chamber that froze.

Whether this was the main issue to your burn down, I have no idea. But, if you get this motor up and running again, you don't want to fill the bellows chamber up with water again. I think it usually shows up when rusty water is being blown out of that hole and/or the bellows spring breaks and makes the motor run rough.