Hello, so I'm working on a Polaris Sportsman 300 4X4, it runs ok and starts real easy but it blows white smoke like crazy, I mean it'll fog up the whole damn neighborhood. Its also an air cooled engine, so that means its burning oil I believe. So I ran a compression test, it was about 155-160 PSI cold, and warm I believe it'd be maybe a few PSI more? I believe that is pretty good compression for it right? I thought it'd be more like 120 or less and be rings or something. So what do you believe could cause this? Diesel in the fuel? Pre mix? That is a slight possibility as it is not mine [yet!], but its very unlikely. I will flush out the tank anyways just to be sure. So what would cause white smoke with good compression and air cooled, IF it has clean gas?:huh Also, just for reference, I'll tell you what I was told when this happened. So this is a ranch quad, it was used to pull manure trailers up a steep dirt road everyday [30 horses shit!], and twice a day pulling a trailer with a heavy load of hay for the horses all over the place. And the guy just floored the shit out of it going up the hill every day, and being aircooled and only 300 cc, and especially on wet days, its possibly pulling between 600 and 1,400 lbs+ rider weight, up a very steep grade to the manure pile. NOt good I'd Imagine. Now they use a Honda 450, I still think a 600 or so would be more suitable. But one day, the lady was driving it and it just started smoking like that, I believe, it wasn't a gradual thing. Its only a couple years old too I believe. It's been sitting about 1 year now. Oh, also, when I pulled the plug to do a compression test, it was very wet and oily so it is got to be some oil? And when I shut her down, the muffler smokes a tiny bit of white smoke for a couple minutes when its warm, almost like the muffler is burning it's own small bit of oil. Any ideas? I appreciate any help or ideas.