I have an opportunity to buy an extremely clean 99 Polaris 500 for $1000 (asking price). I currently have the quad at my house trying to check it out before I buy it and this is what I've noticed so far.

When I picked it up Saturday night it would barely run, smoked and sputtered. I got it home and got ready to pull it off the trailer and it fired right up and ran great. Ran it on Sunday around the yard and it ran great again. Got it out after work today and my wife took it while I road my 02 500 and after 10-15 minutes of riding it was smoking and running like cr-p again. I towed it back home and put it back in the yard, and after putting mine up and eating dinner... it ran great again for a minute or two, then like cr-p again. If I start it and run it full throttle there's a lot of missing, sputtering and smoke.

The previous owner drained the fuel and just put fresh gas in it... but with all the smoke I'm suspecting something more than bad gas. My logic is more along the lines of a vehicle, but I would think these are similar. I was going to do a compression test to see what's going on inside the engine, but wanted to get your thoughts? Could it be something internal leaking oil or coolant in the engine that would cause it to run bad. Buddy who works on ATV's (but not Polarises) says the carb needs to be gone through. I nervous I'm going to buy this thing thinking it's the carb, and finding out the engine is shot or it's got some electrical issues.

Again, the ATV has moments as many at 10 - 15 minutes of greatness, but you never know when the rough running will hit, which is why the guy bought a new one and is selling this one so cheap. I hate to walk away from it being in such good condition though.

Your thoughts please???

 

OIL smoke (WHITE)? If is then possibly loosing compression when gets hot and oil getting past piston rings and burning. MAY be time for a new top end,valve guide seals,etc OR could be GAS smoke(BLUISH) from engine flooded from worn needle valve in carb,check oil dipstick, see if oil smells like gas or overfull (another sign) What ever,DON'T leap into buying this machine unless you like working on em! PS plus NOT my favorite year model,cam problems,u-joint drive shafts,etc. Unless its almost a give away,I would look for a later model,less over all problems (depends on maintenance) OPT

 

could be the cam is getting bad as they were known for it w/ the lobes rounding off in those years i beleave.

 

check the air box and filter for gas, like opt said ,might be bad needle valve in carb, flooding it, is there any gad runnin out the bottom when stopped?