My father-in-law has a 500 H.O. and its been a pretty good quad till lately. All of a sudden it has started smoking and I mean smoking BAD!!! It makes my 2-smoke look like a hybrid LOL. So far we checked the oil and it is where it needs to be, checked the crankcase breather hose for back pressure and its fine. Tried a compression test but didnt take the head cover off to disengage the decompressor. We read 75 PSI at that. Any other ideas?? It doesnt really seam to be running any differently power wise.

 

It is burning oil because the rings are bad or it is burning coolant because the head gasket is blown.

It it is blue smoke it is oil. It it is white smoke it is coolant.

 

If a person was to have to rebuild a 500 H.O.. Anything anyone would suggest to do to it upgrade wise while being in there?

 

Also the float needle in your carb could be leaking and letting gas get into your oil. That will cause them to smoke.

Check your oil.

 

Sounds to me like your oil ring has worn itself flat... how many miles are on this machine