Alternator wire dilemma

[aerojack7654]

Hi Folks,
Another dilemma as I gradually bring my 350 back to life - alternator wires. It seems that the alternator wire bundle exiting the case has the normal 2 yellow wires, an expected red wire, and an interloper that is not explained by any wiring diagram I can find - a blue wire, all with the same blade connectors. Is the blue wire some sort of neutral switch output or some other mystery?

Thanks for your help,
Jack

[Jordan]

Sounds like you have a Motoplat alternator stator in your engine. It was one of the two electronic ignition systems fitted to singles.
The blue wire is for the CDI ignition, it provides some hundreds of volts to charge a capacitor.

If your bike has points rather than CDI, just don't connect the blue wire to anything, but make sure you insulate it - couple of layers of heat shrink tubing should do.

It's quite likely the blue wire is dead anyway, as Motoplats aren't famous for longevity.

[Ventodue]

Sounds like you have a Motoplat alternator stator in your engine. <snip> It was one of the two electronic ignition systems fitted to singles. The blue wire is for the CDI ignition <snip>

Wired like this ...

It's quite likely the blue wire is dead anyway, as Motoplats aren't famous for longevity.

The main problem seems to be the stator coils - which can be re-wound.

[aerojack7654]

Thanks so much for the info on this, at the very least I won't electrocute myself! I was hoping to convert the output to 12 volts with the appropriate R/R, I assume that I can still try it. The motor (and frame) that I bought originally came from an estate in Florida - the original owner had this motor built at Eurotech in Florida for AHRMA racing in '92. It's got over 4k of '92 dollar receipts in it and hasn't been run, it was very well preserved though and inspection has shown that the internals are in very nice shape. I did get some other bits with the bike including a new Rita electronic ignition and a kit from somewhere that includes instructions and a diode for 12V conversion. I'm using a Sachse ignition (I'm familiar with them and like the adjustable advance) and a Kohler R/R so hopefully that'll be enough to charge the Lipo battery. It's still aways from motor trials (I have more questions that I'll be posting soon enough, see progress pic -

small ducati.jpg

), but I'm starting to plan out the wiring harness and that blue wire has been a conundrum.

Thanks again for the help!

[Ventodue]

No worries. Tell me, does your engine number start DM or MD? And how many fins are there above the exhaust port?

[aerojack7654]

The engine stamping is DM350, and there are 8 fins over the exhaust. Someone put in a different alternator?

[Jon Pegler]

Come on now Craig, keep up.
Widecase motors are all stamped DM , unless someone knows any differently.
What does it say on your Vento?
I'm fairly sure only Mototrans narrowcase have MD.
Too many people think the only way to tell a Spanish motor is if it's stamped MD.
That Motoplat alternator with the blue wire was fitted into the 350 Road motors.
It could have come out of one of those.
It's a bit difficult to make out if Aerojacks motor has a Spanish head from his photo.

Jon

[halfpast]

Pardon a slight change of subject - Aerojack what type of wheels and tires are those?

[Jordan]

The main problem seems to be the stator coils - which can be re-wound.

I found another way to more easily repair a burnt out Motoplat capacitor charging coil.
Rather than deal with the potting resin, I used a Ducati 6 pole stator that isn't potted - the coils are exposed and readily accessible.
Remove one of the coils (they are all with thick wire, meant only for battery charging) and fit a CDI charging coil made for Vespa scooters. They have the correct dimensions, as their alternators were supplied by Ducati.
It appears still to make enough volts to charge the battery at reasonable revs.
There are a couple of variations to these CDI charging coils, and it's easier to fit the smaller type (no machining needed).
They made Vespa copies in India, and these had Indian made copies of the Ducati alternators too. Very affordable!

I also fitted a copy CDI unit/HT coil, also low priced.
The bike is an easy starter now. The only Motoplat part of the system now is the magnetic pickup sensor on the right hand side of the engine.

Disclaimer: This is all very recent, so I can't report long term success, but so far it's promising. Nice to be able to fix my Ducati with pocket money for a change!

[Jordan]

I was hoping to convert the output to 12 volts with the appropriate R/R

For 12 volt operation, run your alternator in 2 wire mode. Just use the 2 yellow wires, and not the red one (insulate the R-R end).
I think you can use most common Japanese motorcycle 3 phase permanent magnet type rectifier-regulators, using 2 of any of the 3 inputs.
These would all be likely to be able to handle the power output from a Ducati single, and will regulate for a 12V charging system.

I'm trying a R-R made for a small tractor. It has a wire for a charge indicator light that goes out when the engine starts, which is nice.

Like this one: Ebay item 271497547836