Question on 67 MK3 Charging System

[tonyduc]

I am trying to determine which magneto alternator system I have on my MK3. Reading Tom Bailey’s Workshop Manual it should be 6V 40 W, no battery system, HT coil in AC. My project bike when I bought it had the wire harness cut from the headlight to alternator wires, everything else is missing, so I am trying to confirm that I have the above before buying all the parts I need. So there’s 3 wires from the alternator, the stator has 2 feed coils (page 98 of Bailey). Does this appear to the MK3 system?

Also the rotor has an inscribed vertical line, does this imply a certain alignment when reinstalled?

Thanks
Tony

[George]

Unable to answer electrics questions. I believe the inscribed line is for balance and should be lined with top dead centre, in other words in line with notch on end of crankshaft

[Jordan]

The scribed line on the alternator rotor is important for the AC "magneto" ignition systems on Ducati singles with points but without batteries.

The purpose of AC alternator timing is to arrange it so that the points open when the AC sine wave is near its peak voltage, to provide the best possible spark.
It is used with an automatic timing device (advance-retard, spring loaded points cam) that has a narrower operating range than those on battery type ignitions.

There is information on this page: http://www.motoscrubs.com/Duc_Technical.htm

[ducwiz]

Here http://www.motoscrubs.com/Ducati_Electrics/Ign_Flywheel.htm is the precise description for the alignment of the inscribed line.
Your bike seems to be the n/c MkIII model, battery-less system with magneto ignition.

cheers Hans

[tonyduc]

Thank you all for the help. Yes, it does seem from the flywheel and 3 wires coming from the rotor, that it is a typical MK 3 wiring - magneto without battery. What threw me off was the wiring in the headlight (which has a speedometer like the MK 3), it has wiring typical of the alternator scheme http://www.motoscrubs.com/Ducati_Electr ... ematic.jpg, with a 7 wire terminal block and two other fuse terminals shown in the alternator scheme. So it is likely the headlight was swapped from another bike. Like I mentioned the wiring between the headlight and magneto was missing so the rest was guess work. So I will wire it according to the magneto without battery scheme and just ignore wires not used in the headlight.

Tony

[Bevel bob]

I would have thought a 67 mark3 would have had a later alternator 60 watt 3 wire and a battery system. Might help if you could get the numbers inscribed on the advance and retard unit behind the points. But be carefull, easy to lose the timing of valves and ignition!!.