While a one cylinder engine is running, an intermittant “poofing” sound is noticable. The sound is particularly noticable when the engine is slowed-down.
What is the cause?
A long time ago, my father bought his first fishing boat, for salt water fishing.
It was 26 feet long, a hull shaped like a canoe with a pilot house on top and came with a motor he called a ‘one lunger’.
In actuality, it was called an Easthope marine gas engine. (1949)
You started it by setting the fuel and spark and turning the big front flywheel (by hand) up to full compression.
At the top of the stroke you turned the flywheel as hard as you could to get the thing to fire up.
Some times you could work up a good sweat with this rig.
You had to remember that if you didn’t remove your hands quickly after turning the engine over and it backfired, you could wind up with a broken arm/wrist or shoulder.
That was the pitfall of those engines.
But if you kept the engine tuned and you kept draining the water from the (gas) glass sediment bowl that engine would run all day without a hiccup.
I guess the best running engine sound from that one would be: ka-chuck, ka-chuck, ka-chuck.
The 'poofing sound came from his too and the mechanic (at the logging camp back then) said it could be from excess air being compressed.
I couldn’t tell you if that is true or not.