Ski Doo 440 Question

[yam2stroke]

We got an old Ski Doo TNT with a bombardier 440 engine in it. I'm not sure what year it is, somewhere in the 70s. My dad melted a piston about 15 years ago and parked it. Then my bro rebuilt it about 4 years ago, which was before I knew anything about engines so I didn't see the insides. He gave up cause the carb was messed up and wouldn't pump gas. Last summer, I played with the carb and got it to pump, then didn't touch it after I bought the shee. Today, I went out and messed with it since we had no school and the snow is too deep for quads. I got it to run, but to keep it running I had to keep playin with the choke. It tried taking it for a spin, and it would barely move, as soon as the clutch engages it just bogs, and it kept backfiring. After riding about 20 feet, I realized I was covered in gas. For some reason, it is blowin air and gas out the carb instead of sucking it in. Now when you open the throttle and look through the carbs, you can see straight into the intakes and see the pistons. Do these engines not have reeds??? What is supposed to keep the pistons from pumping air back out? Does anyone have any ideas whats making it blow out of the carb and backfire? Any help or ideas are appreciated.

[bobeaser]

The Rotax engines have a rotary valve. If that was taken apart the rotary timing could be off which will cause major problems. What type engine is it? Here is a photo of how it looks

[yam2stroke]

All I know is that its a bombardier 440.

[Maico]

You've got an early Rotax engine. There were no reed valves or rotary valves back then. They came later. You need to find a simple carb rebuild kit. They're dirt cheap. Carb should be a Tillotson.