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Discussion Starter #1
This weekend a buddy of mine melted a piston. He rides a 02 xc500sp. The piston on the PTO side is the one that went. Right now I am not sure what caused it. I also ride an xc500sp and so does my brother and all three are setup exactly the same as for jetting and clutch setup. However when I pulled his plug I noticed that he was running a NGK BPR9ES. I run the stock plug Champion RN57YCC. As soon as I saw melted metal I pullled the plug on the other side. It looked good. Does anybody know how the BPR9ES compares to the RN57YCC? My first though was that the NGK is a hotter plug but I dont know. I forget the jet setting on the carb. The temp outside at the time was 16 to 20 degrees and I am located in Michigan don't know the elevation. Another question does anyone know why the PTO side is usually jetted richer then the other side? Any help would be great.
 

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i think that is the right plug, he could have got bad gas with water in it and plugged the jet, on a rebuild like that drain the tank, inspect the inside for debries, like ice, pull the carbs and have them checked, when you drain the gas pull the tank right off the machine and poor the gas into a clear can if there is much water in it you will see it seperate over night. DO NOT JUST REBUILD THE ENGINE, FIND WHAT CAUSED IT.

if you others filled up at the same place he did i would drain all the tanks and check the carbs,
 

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Check his main jet too in carb on side that burnt, it could have a piece of dirt or something stuck in it. Had a pal with a brand new MXZ 500 that had that, melted a nice hole in one piston too!!
 

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Discussion Starter #4
Just to give you all an update it was not a melt down. The exhaust valve broke into two peices. One hit the head and piston. The other half took out the crank and the case. Thank goodness for the 2 yr engine warranty. Polaris is fixing it under warrany. Also have another friend who had the same problem with his sled, it only had 50 miles on it. However he had ported it so he voided the warranty.

Is this a common problem with the VES engines?
 

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In my '99 500 XC I use the BR9ES's.
Mine is not an SP, no vavles, and now glad of it.
Boy...good thing for the warrantee...would have sucked for your buddy.
 
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