I have a 1990 polaris trail boss 250 that was just rebuilt because the oil injection broke. i am now mixing the gas and oil 32:1. but after i run it hard for a little while in the mud or to pull out stumps the motor likes to run really weird and backfire a lot. it almost seems like it over heats and its making me nervous about blowing it up. any ideas.

p.s. its air cooled

 

Drop the ratio down to 40-1 instead of 32-1. You're using way too much oil. You can starve an engine for octane and actually cause one to over heat! It just needs a film of oil in the mixture to oil the rings,lower rod bearing and crank bearings.A lot of people think more oil the better,but it's not.The mixture isn't burning properly,you're not making the horsepower the engine is capable of making and it will run crappy and overheat at times.

 

i never heard of to much oil causing over heating. and i build peformace mopeds.

 

But it can! You loose octane which helps the engine to produce the power it's capable of making by diluting it with too much oil,along with it running hotter.I know this is against what a lot of people believe! 32-1 ratio is what we normally ran in higher compression KTM 2 strokes that required it. On more heavily modified engines for our motocross and enduro riders we sold VP 108 octane that a lot of them mixed 50/50 with 93 octane as regular pump gas could and has done some serious damage used alone in these conditions.Some would increase to 30-1 on the ratio. This I learned first hand from Dick Burleson and also backed up by Malcolm Smith when they visited our shop years ago along with some of the older riders before my time. I thought the same as you,but learned otherwise and who am I to dispute two of the best riders in the world?