Exhaust popping when retarded

[TH47Indy]

FINALLY finished up the resto of my '47, thanks to the advice from many on this forum.

Started it today for only the second time, and when the ignition is fully retarded there's a steady, somewhat slow, popping sound from the exhaust. I did not notice this during the first time starting it.

Any suggestions or ideas on what's causing this?

[T. Cotten]

TH47Indy!

A retarded spark occurs late, and that's probably what you hear.

Running a machine retarded turns the pipes pretty colors, too.

The cure is to advance the spark as it should be: Retard to kick it, then advance to go.

....Cotten
PS: Please beware the timing marks weren't always as accurate as other marques....

[TH47Indy]

TH47Indy!

A retarded spark occurs late, and that's probably what you hear.

Running a machine retarded turns the pipes pretty colors, too.

The cure is to advance the spark as it should be: Retard to kick it, then advance to go.

....Cotten
PS: Please beware the timing marks weren't always as accurate as other marques....

Thanks Tom!

Only retarding it to put it in first gear, and pretty sure it wasn't there during the first start.

I'm now thinking that it may be bad gas. I was lazy and anxious to start the first time so just put a little gas in from a can that may have been around a while. That was a while back, and now it does smell like it may be older than I thought.

Drained it, and will be trying a fresh batch.

[T. Cotten]

I always retarded to get into 'first', of course TH47Indy!

Its all bad gas, and I live for it.

Indians were the only machines I couldn't "strobe".... That was disturbing.

....Cotten

[pisten-bully]

TH, not sure if I've ever heard the same thing, BUT ...whenever I've been slow to advance things I've sometimes felt it was sort of "puffing" when retarded (hard to describe) and I think it's more pronounced in cooler weather. Goes away when I advance spark.