I bought a 2003 Polaris Predator 500 a few weeks ago and it wont run, the guy i got it from left it outside in freezing rain for a week and he claims that it ran fine before that, the machine has good spark and 142 pounds of compression, it will fire if i squirt gas into the carb, it also backfires alot i dont know what to try next any help would be appreciated

 

Sounds like a fuel related problem, pull the carb and clean it, and drain the fuel tank and add some fresh gas.