[wwest]

As everyone already knows the CDI is highly subject to alternator voltage spikes, anything on the "12 volt" supply above ~15 volts and the SCR begins to "self-fire" (tach jumping, etc.). This looks like it might be an input voltage "snubber" to "sink" any incoming voltages above...12 volt zener plus 2 diode drops....~13.2 volts. Might have been used with a ~0.5 ohm 10 watt external resistor.