OutdoorKing Repair Forum Forums Finding and Swapping Rare Finds & Donations Briggs 81700 - Wind-up Starter - 1960

I suspect it is a six lobe knob sticking out the side.

I think this is an interesting story - vintage mower wise.
Briggs developed a safer system than the original Tecumseh 'impulse'.

The impulse system was a 'wind and flip-over' crank handle.
One safety concern (I guess) was that a child could crank the motor inadvertently.

The Briggs system introduced the rotary knob release, so cranking was
a two-stage process. Note, though, that the high-energy spring was
still a safety problem (in service).

Here is a wonderful 2013 auction photo(s) of NOS:-



I think superdooper has a significant engine here -
for early design of rotary 4-stroke engines.

Crank or cranky? You decide.
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Jack