I just picked up a Polaris ATV, (prev owner said it was running when parked 3 yrs ago) it appears to be in very good cond, but after getting the float unstuck & cleaning up all the gas it will not stay running for more than a cpl mins & stumbles when you accel. I am also getting some white smoke from the exhaust. I am familiar with Mikuni carbs & pulled the cap & slide out, fuel line off & vent hoses sprayed carb cleaner in all orifices, mainjet & fuel inlet & all seemed to be clear as the cleaner did exit from somewhere else on the carb? but to no avail runs for a few mins then dies & will not restart unless you wait 1/2 an hr or so .. Any ideas or suggestions would be greatly appreciated also the white smoke worries me ....

 

Check compression. If 115 psi or lower probably time for at least a new top end and don't forget the crank seals that have been sitting in gas for 3 years also.Smoking is usually unburned fuel/oil mixture escaping past the piston/rings and burning in the exhaust pipe.Another sign of weak top ends is dieing after it warms up and won't crank back up until cooled down which you mentioned.