Usually there's been evidence of excess heat on the exhaust side of one piston. The last time it went it looked like this, completely washed away on the exhaust side of the crown:
__________________
Formerly known as 63November, and before that as Golsovia.
Current:
-97/98 Polaris Trail RMK hybrid with over 40,000 combined miles
-99 Arctic Cat 550 Panther 14,000+ miles
-01 Polaris SuperSport 5 rebuilds
-340 eBay Edge from AK, and 10+ other states
-'11 AC T570 brand new...1700 miles
Last edited by 162Whiskey; 03-30-2008 at 12:19 AM.
Thats certainly not a typical 550 failure. The vast majority of 500 engine failure in these late model engines is intake skirt scuffing from lack of lubrication. If you have had repeated failure of the type pictured I would urge you to swap out the CDI module and/or check the squish before running it again once rebuilt. It's obviously not lean as many of these engines get as low as 9 mpg.
I haven't heard of any locally getting poor fuel mileage, not even the "Tank Tourings." And mine has been good about doing up around 12 or better. That said, this was an overheat deal at right around the freezing point and it is/was jetted to handle -20 - which it had done under load less than a month earlier.
Yesterday, with threatened forecasts of warm temps for the week along with rain, I needed to retrieve my 550 AC Panther from the next town over - which is 71 miles away. At ambient temps of 40 F and wet, heavy snow on the trail, the same 550 pictured above dragged that machine along with a 100-200 pound sled hooked behind the Panther most of the way. (An 800 pound load conservatively IOW.) The engine did run hot some of the time - including the crankcase when I checked a time or two, but it did the job and came back in one piece.
As warm as the case gets on these 550s sometimes, I almost wonder if gas expansion and a subsequent lean condition might result as the air and fuel are pulled into that high temperature chamber. At the very least it would seem that a very high fuel mixture temperature might lead to combustion timing problems as the overly pre-warmed mixture gets delivered to the combustion chamber.
I have wondered if it would make sense to cast radiant fins on the crankcases of these 550s to better keep the case cool just as some liquid cooleds do with their coolant passages.
__________________
Formerly known as 63November, and before that as Golsovia.
Current:
-97/98 Polaris Trail RMK hybrid with over 40,000 combined miles
-99 Arctic Cat 550 Panther 14,000+ miles
-01 Polaris SuperSport 5 rebuilds
-340 eBay Edge from AK, and 10+ other states
-'11 AC T570 brand new...1700 miles
