CDI unit - "transducer"

[penman]

Tearing my hair now trying to find the fault with my K2. I have been examining the two transducers. According to the diagrams I've seen, both the green (magneto) input and the red (pickup) inputs go directly to diodes, so if I connect an ohm meter with the negative on either of those, It should indicate infinity to earth (reverse biassed). If I connect the meter with the positive to the input I should see a forward-biassed junction plus other components. In fact on the red terminal I am measuring 557 ohms either way round, and it's the same on both units. On the green terminal I see 118K to earth either way round, again the same on each unit.

Can anyone tell me if these readings are correct or not? These are the grey transducers, are they different to the ones which we have diagrams for?

Another question. The kill switch works by earthing out the magneto output (green). But the ignition switch earths it via a diode - not sure why, unless it's to give a bit of protection to the magneto coil on the average switch-off? This diode by the way is bodged into the wiring with a bit of choc-block - presumably that's the work of a previous owner?

Sorry about the questions, at the moment I don't know what's right and what's wrong!

Regards.

[EVguru]

I'll just deal with the second question for now.

The diode is to protect the ignition boxes from battery voltage. A DC voltage from a low impedance source (battery) would cause the SCR to latch up when triggered and burn out. This was common back in the day when rescue services were called and found there to be no power to the ignition system and patched in a temporary feed. It could also be caused by a faulty ignition switch.

The diode arrangement is OEM.

[penman]

I'll just deal with the second question for now.

The diode is to protect the ignition boxes from battery voltage. A DC voltage from a low impedance source (battery) would cause the SCR to latch up when triggered and burn out. This was common back in the day when rescue services were called and found there to be no power to the ignition system and patched in a temporary feed. It could also be caused by a faulty ignition switch.

The diode arrangement is OEM.

Thank you, interesting! So the diode simply protects against someone mistakenly thinking the green to the ignition switch is a battery feed to the ignition - and "fixing" it!

I should have mentioned that all my measurements given earlier were with all wires disconnected.