The Johnny Popper had a big, external flywheel on it. If I remember correctly, we opened those two little cylinder valves on the side to keep the pressure down enough to start it. We used our hands to spin the flywheel to get it firing. Fire would spit out of the two valves on the side, and we’d flip those shut. Then *pop* *pop* *pop*!
Ya, the early ones started by the flywheel. And you had to open the decompression valves like you said.
But to let that GD magneto get ahold of you..MAN! Just about the time you could get away it would nail you again.
NEVER...mess around by the spark plugs when its running. EVER.