Moto Guzzi V700, V7 Special, Ambassador, 850 GT, 850 GT California, Eldorado, and 850 California Police models
Thanks to Ralf Brinkmann for sending me this information. Ralf is remembering much of this from an extract of a schoolbook. In Ralf's own words:
Some years ago with my Guzzi I changed to the blue Bosch coil - so last year I gave away all my black Bosch coils to the owner of a BMW-Isetta. I collected these coils over the years when I had air-cooled Volkswagen's - so I'm not able to measure but they all differ a little bit in size and resistance.
But I have a chart for you. The chart compares the black (E), the blue (K), and the red (KW) Bosch coil and shows how fast a modern transistor driven coil loads. In this chart the Guzzi engine would count as 3-Cyl. due to the asymmetric arrangement.
The lower the the resistance of the coil the faster the coil loads up to a definite voltage line - important at high engine speed.
The limit for the breaker points is the 5A line. For this reason the red E-coil needs a fat 1.8 Ohm resistor in series connection. The resistor may be shortened by a relays while starting.
If you want more amps you must use electronic components. Modern Guzzi coils - e.g. Jackal - have less than 1.0 Ohm resistance in the primary circuit.
In combination with the breaker points the powerful 4th coil will need something like this: Steuergeraete fuer Zuendanlagen mit Unterbrecherkontakt und Fliehkraftverstellung
These breaker point driven TSZ-U (or TSZ-K) controllers do not close the primary coil circuit for a fixed angle but for a fixed max. time - maybe 4 ms - depending on the coil - in German calledautomatische Schliesswinkelregelung
I wonder if the tiny Guzzi distributor cap would survive the high voltage - maybe one day I'll ask the FIAT-500 club.
- Schoolbook extract (see page 544)