what else besides a clogged muffler makes a moped backfire?

Re: Backfiring

The timing being off.

Check and set your points.

Cleaning them wouldn't hurt either.


Some ideas

John Lieberman /

I'm no expert, but I've got some experience with my own backfiring.

Once it was caused by too rich a fuel/air mixture. More gas was going through the cylinder than could be efficiently burned, so it collected in the exhaust until it blew up with a most convincing racket. It ruined my exhaust baffle.

Another possible source is bad gas. I tried using some gasoline from my two-stroke snowthrower in my moped. I normally use 32:1 to 40:1 gas/oil ratio in my bike, but the snowthrower gas was 50:1, using some kind of synthetic lubricant that came in a little plastic packet. Further, the gas was a year old.

The moped backfired repeatedly, but stopped when I drained out that fuel and refilled with the normal stuff. I never did determine if the backfiring was due to (1) using a mixture that was too light on the oil, (2) using a lubricant that my Minarelli engine just didn't like, or (3) the gas had gone bad.

Good luck!

Re: Some ideas

It could also be a gap between the tailpipe and the exhaust manifold, or a hole in the tailpipe.

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