strange problem

[apex yooper]

After changing donuts, sled still backfires. I took it for a test ride, drove it to my loading ramp, and turned it off. A half hour later, I started it to load on trailer. There was what I thought was a major exhaust failure. It sounded like a wide open exhaust.

After thinking about it, I remembered I heard that noise before. After changing donuts, sled wouldn't fire up. even with a shot of ether. I had the air box open, and tried starting it with wide open throttle. I thought it might be flooded. It started up, but the sound out of the intake sounded like the exhaust. It went away, and sounded good after that.

If this is the problem again, what could it be caused by? I was thinking something in the fuel system is flooding the engine.

 

[LJ 452]

If you hadn't run it much give it a some time. I changed my donuts and left Y-Pipe last weekend and finally got to fire it up and ride it last night. It didn't back fire but it did have smoke coming out around the riser and pod, also it still idled funny. I figured it may me some air still in the fuel lines and or the donuts seating in. Of coarse the smoke was from the Y-Pipe and donuts change, release agents on the donuts and risidual P.B. Blaster from me trying to get everything apart. We'll see if it goes away.

 

[sobfrogg]

Have you checked the timing? Or how about checking valve clearance or cam timing?

Not saying that is it. With other engines I have worked with this has been a solution.

A fouled plug can also cause backfiring.

 

[obile]

do a diagnostic on your tps sensor. when they go bad they default to full rich telling the ecu to dump massive fuel to the engine. itll pop and sputter and run like crap.. had this happen twice now. got a new one coming again.