"You have a magneto with point
"You have a magneto with points and condensers.
The ignition switch will have these terminals.
B = 12 volts from the starter solonoid
S = Start; Sends 12 volts to the primary on the
starter solonoid
M = Common; there will be two M terminals. One
is ground, the other is the wire that grounds
the magneto to turn off the engine.
C = Choke
A or I = Accessory or 12 volt ignition. You
probably do not use this one unless you
have accessories to power from the
switch. Some arrangements have a
separate choke switch which would get
power from here.
The wire colors could be anything by this time so I did not mention them."