I have a 1999 polaris sportsman 500 my problem when at a idle and in neutral if you max thumb throttle engine will bog down and miss like crazy but still stay running it will also back fire through the tail pipe. if you hold throttle all the way for about a min the engine will pick up and idle fine . then die maybe carb problem need some advice

 

Welcome to the forum! If you can pull the valve cover and check the exhaust cam lobe(or lack of one if it's ground down!) sounds like the same old soft cam problem from all the 96-2000 model 425 and 500 engines! Not trying to sound harsh,but this is a common problem! Especially the popping back! They usually will crank and idle good,but wont accelerate. Plus you can check some back posts on this. If it happens the cam is fine,then could be just needing a good carb clean or rebuild? Just pull the valve cover and give it a good look,plus valves set at .006! Keep us updated. OPT

 

simple thing would be a dirty carb. not so simple is what opt mentioned, which they have been known for, is the bad cam.