81 2pg backfiring only when cold starting

[frodrummer]

Like the title says. I have to use the choke to get it started...which is not my concern. While trying to start, it backfires at least 2-3 times until it gets warm. This only occurs during a cold start after sitting overnight, or for a day or two (even in 90 degree weather). After its been run for 40-60 seconds, it runs perfect and doesn't backfire at all no matter how many times you stop/start it. The carb spring is good, and is adjusted to allow the "click" just prior to throttle movement.

I'm assuming its gonna be a carb or spark issue, but not sure. Could I be getting some sort of fuel dump when cold starting? Or is this a symptom of a spark plug gapped incorrectly?

The backfires are not loud, just a quick "whoosh" of air (type of sound).

Please let me know if this situation sounds familiar. Thanks in advance!

[Heliarc]

I'm not sure, but does anyone know if this engine has reed valves? If they're weak they might be letting air/fuel blow back through the intake until the engine catches but that's a wild guess.

[frodrummer]

Yes, its got reed valves. Changed out the spark plug, gapped at 30. Had an exhaust leak at the jug, fixed that as well. Still acting the same.