Hi have this polaris that started running terribly. The air filter was pretty plugged from riding dirt trails. We hoped that by cleaning the air filter and the carb that the thing would run good again. SO far, I've put in new piston, rings, wrist pin, gaskets, honed cylinder, retimed, and adjusted valves and cleaned the carb twice. Still missing and spitting, but he compression is back up. Any idea??

 

Compression should show between 55-90 psi on average because of the compression release device on the cam.Some may show a little more. Never been a fan of cleaning carbs. You've had it off twice now,shouldn't have to remove one but once and rebuild it with a good kit.https://www.ebay.com/itm/New-Shindy-...ZRw15S&vxp=mtr This will eliminate any doubt on the carb. Float level setting is critical on this model. Read this section on the BST40 carb. Used on a Ktm but similar and goes into good detail on setting the float level correctly.The BST-40 Bible | Adventure Rider
Also check that you have good flow from the fuel pump. Pull the fuel line from the carb and crank the engine over. Should be a steady or pulsing stream of fuel. If it's weak the fuel pump may be the problem. If you still have problems an old method of checking if it's an electrical miss is to use a timing light. If the light flashes in unison with the miss it may be an electrical problem.That's where the ignition section of the manual would come in handy with the checks and trouble shooting checks.If you don't have one.2012 Polaris Sportsman 500 H.O. Service Manual PDF Download