As I attempt to start my prairie 300, I have just noticed that it pops back into the air filter on each stroke. If I continue to turn the starter, it will eventually start the engine with the throttle partially advanced. Any suggestions on what I should do to correct this? I have tried it with various choke positioning and it makes no difference. It still takes a long time before the engine catches. Once running, I have full power. It will idle sometimes after starting but not for very long. I have also put new fresh gas in the tank, checked the filters and screens, opened up the carb. and made sure that it is clean. ports all seam to be open and working.

 

Did you remove the jets and blow them out? If not could be the problem.