Did she blow up?

I would go with SPI's. Wiseco's require a lot of warm up in order to keep from squeeking a piston (which you should be warming them up anyways but Wiseco's need it EVERY time or you run the risk of it sticking again). I just rebuilt my Edge 600 and used SPI's. They are on Ebay for about $140 or so for the set. Real happy with them so far, about 200 miles on the sled and still running strong, granted I rebuilt the bottom end at the same time.

That thermostat looks like it may have stuck and someone may have tried to wedge it open (probably the previous owner). I would replace the stat while you're in there as well.

Just found this thread looking for info about what happened to mine, and I saw the exact same thing with my thermostat. A girlfriend of mine was riding my '05 800 RMK. She's only about 5'2" and apparently didn't see the temp light come on over the handlebar (with riser). I came back down the trail looking for her and found her with steam pouring out of the head around the spark plug holes like Old Faithful. Long story short, when I pulled the engine apart, I found that exact same little metal piece stuck in the thermostat. I believe it came out of the center post inside the thermostat, and stuck it closed, just like this original poster.

After a top end rebuild, I've still been having major overheating problem. At first I thought I was still just having air in the cooling system, so I kept burping it and adding more coolant. Finally after struggling with it, I decided there was something more major wrong than air in the cooling system. Pulled the head off again last night and found that it's 8 or 9 thousands out of being flat. I assume it go so hot from the stuck thermostat, that it warped the head.

My question is this. Do I get my head milled back to flat, buy a new factory Polaris head, or buy an aftermarket head? Of course I would love the added performance of an aftermarket head, but not sure about the $ and I want it to run on 91 octane pump gas. Any thoughts?

Possible fine crack in the cylinder that opens up with temp. Exhaust gas gets in the coolant and pressurizes the coolant tank. Had that happen on a motor before. Rode it for a while and the coolant tank pressurizes and pressed against the brake caliper. Brakes slowly went away til I would stop and let the pressure out.

smtt126 said:

im glad you posted nevadarmk after i put my motor back together i too had nothing but issues. system kept eating coolant and always pressurized itself even after it was cold. went to ride it for the last ride of the year and when i fired it up it idled great. but sounds like its hitting a 4k rpm rev limiter. wont move at all under its own power. i pulled the head again and had another fried oring. i put a new set of o rings and base gaskets in it. and that fixed all my coolant issues but it still wont rev over 4-5k rpm and will not move... any ideas guys? i got all summer to fix it now that its 80 and sunny outside.

Click to expand...

When crank bearings are going, they limit both the top rpm but the engine winds up slower.