I have tried and tried again to get my machine to fire. I first thought I flooded the crankcase and kept fouling plugs. I drained the fuel, put in new plugs and still no pop. I have spark from both and I have fuel in the floats, I can pull the machine over about 10 times and then huge backfire. Any ideas? Want to ride bad! This sled has always started very well so I'm baffled.