I bought a 1998 polaris 500(I believe). The previous owners said it needed a new starter... Put the new starter in, replaced the spark plug. It will start and run for a minute after letting go of the throttle. If you hold the throttle it will continue to run. After it shuts off, it wont start back up unless you let it sit for a while.

 

First off adjust the cable slack until you only have 1/8" free play at the throttle lever. Any more than that and the etc contacts in the throttle housing can touch and kill the engine. Also pull the fuel line from the carb,place it in a container and crank the engine over. If the fuel pump is ok you should have a steady stream of fuel.If it's a weak stream or dribble,time to replace the pump. After that check the valve clearance,.006 intake and exhaust and also for a worn cam exhaust lobe.Common problem on 1996-2000 model Sportsmans. You may also need to clean/rebuild the carb,but check the other things first. Get this cheap 5 buck manual as it has good trouble shooting guides and tests for mechanical and electrical problems along with maintenance and general repair help.Better than trying to guess and randomly throw parts at one.1998 Polaris Sportsman 500 Service Manual PDF Download