It started backfired and blew white smoke. Have spark. Have gas. Will not start. Do you have any ideas what the problem could be? Thanks in advance.

 

Could be a mechanical problem,piston/rings,blown head gasket or could even be an electrical problem even if you have spark. Guess you're talking about the Ranger 700 6x6. I'd check for compression along with any coolant leakage around the head to start out with.Even a cam braking where it's milled down for the cam gear can stop one in it's tracks. I've had a couple do this. Beyond that the service manual gives you the best trouble shooting guides to help narrow down what the problem may be. Here's a reasonable one for 10 bucks that can help.2007 Polaris Ranger 700 6X6 XP Service Manual PDF Download