help! what are causes for sled to backfire through carb???

[tntsmallmotor]

2008 skidoo tundra 300f, new crank, piston, sled idles great, soon as u hit throttle sled starts to spitand spudder back through carb? It is a single cylinder, single carb motor..

 

[kootenaycat]

Broken reeds, water in gas is where I would start. Should be a drain on the float bowl, crack it open and catch the gas in a container, you'll see the water in the bottom if there's any