Burning up - need help-550 polaris fan

[wesledip]

Hello,

I need some help with a problem that is plaguing me. First, my wifes sled chunked a piston last year, 2005 Trail RMK. I had both cylinders bored .020 over. I inspected the condition of the other parts. Everything looked good and so pop in a set of Wiseco with new rollar bearing and clips. everything when back together fine. I was pulling 118+ psi on the compression. She recently put 50 miles on it and it died. Well, I had zero psi in the same cylinder as before and thand that piston and cylinder end up toast. I inspected the oil line to that carb and it seemed fine. I get the feeling that the cylinder is not getting lumbrication. Oh I did have the hose off that blow pipe fmistakenly for a short time while starting it up after the new pistons were in. Once I re-connected it it ran like a real champ, that is unitl it bit the dust.


Any help would be greatly appreciated.

Thanks,

Mark

2008 700 Dragon
2003 700 RMK
2005 Trail RMK

 

[fordpickupman]

bad deal

Do a search on here, they had major issues on some of those engines. The stories will make you cringe......

My mother n law's sled did that last year. They fought with the dealer to cover it under warranty, it still only has 800 miles on it. They will never buy a fan cooled again.

 

[BB454]

fan

Did the piston stick in the cylinder or was the exhaust edge burned off? If stuck, I would look at the cooling as well. Could be something under the shroud causing it to over heat. What gap did they machine the cylinders to? The fans have a large clearance spec because the pistons swell up more than a liquid. What ring end gap did you set it too?

Any bubbles in the oil line? If so that would indicate that oil isn't pumping. When you tore it down, was the lower end covered with oil? I guess you could pull the pump off and run premix if you think it's the injection system.

 

[wesledip]

500 trouble $%#@

Thanks for the replys.

i did not see any bubbles in the line and the piston did not sieze up to the cylinder. The forward side of the piston and rings was cracked, burnt and chunked up. As to the bored out dims it was .003 over the additional .020, according to Wisco and Polaris techincal bulletin. Also, there was not excessive or inadequate oil signs in the crank.

I guess I will try to rebuild it again by going .040 over and maybe I will try to rebuild or replace the oil pump. Boy this is a big headache for such a simple engine.

Thanks again,

Mark

 

[BB454]

Piston

You have just described a failure due to detenation. If it was erroded away then I would say it was lean but chunks missing of the piston and broken rings indicate detenation. May have been a bad load of fuel. Ethenol maybe? Could also be timing. Check that when you get it back together. Also make sure there is nothing in the pipe. (Mr. Mouse?) I would run some oil in the gas in addition to the oil pump on the first tank and see if you can get it to stay together. Might smoke a bunch but you will know it's getting lube.
Also after you get it back together, you can squirt WD40 around all the gaskets and seals while it's running and if the RPM changes then you know you have a air leak but again it would erode the piston not break it.

One more thing make sure the top and bottoms of all the ports have a .5 to 1 mm bevel on them to prevent the rings from catching. With a fresh bore, they some times don't get beveled enough.

 

[wesledip]

BB454,

I will take a look at all you described. Thanks for you advice.

Best of luck.

Mark