This video by Machine Design magazine shows what is wrong.

The detent plunger was too short and it's spring too weak to firmly hold
the switch in the "run" position. So, extra weight on a keyring could
turn the ignition switch off. (By swinging I suppose.)

http://tinyurl.com/mdx67rn

Jeff

--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
The speed of light is 1.8*10^12 furlongs per fortnight.