I'm working on a Polaris xplorer 250 ( I think, I haven't researched the cc or year yet) and it runs and idles well but after about 30 minutes of riding it just bogs down and shuts off and you have to wait a few minutes before starting it again. It has 120 lbs of compression when it's cold and 110 lbs of compression when it gets warm and shuts off. Any ideas on what's wrong? Is it the compression? Or fuel? Or spark?

 

Pull the plug when it dies and ground it against the head to check for spark. If in doubt try a new plug. Compression is kinda on the low point at 110 psi.This may still be the problem if you have good fuel supply to the carb and spark. Just pull the fuel line from the carb to see that it has a good flow.Common symptom on machines that had too much piston to cylinder clearance is that they would start and run for a while then die when rings started loosing sealing against cylinder walls. Would crank back up when cooled down and would do the same thing a little later on. Also check that the tank vent line is clear,no kinks and the carb atmospheric vent is open also.