I got an 05 90 Sportsman ..Sat up for about 3 yrs..put a new carb on it..new plug..not to easy to crank but when it does have to run full choke and wont run barely above an idle..has 90 PSI compression as well...Spark on the plug is orange not blue..Could this be a weak stator or coil?

 

Service limit from the manual shows 115psi for it to run right.Getting kinda low.Does it have good spark when you ground the plug? A lot of these little ones built up carbon, can restrict the exhaust pipe especially around the head making them impossible to run right. If you don't feel a good bit of exhaust pressure I'd clean the exhaust pipe first. Make sure you have good gas flow to the carb. Stators can weaken because of all the dirt they allow in through the covers. You might try to clean the flywheel and pick up coil also. If this doesn't help then check the stator resistance. Black wire from stator to w/r should be around 450 ohms,black to b/r should be 800 ohms,black to y/r 0.5 ohms,black to white 0.6 ohms. Black wire shouldn't short to ground. If stator checks out may just need a new top end. Plenty of them on ebay.Polaris Sportsman 90 Cylinder Piston Gasket Top End Kit 2001 2006 | eBay