Alternator Wires

[Duccout]

Calling all electrical aficionados!

I have my Mototrans 250 engine in pieces, dealing with various issues, and another one to appear is the alternator wiring. Electrics are a black art to me, so I would appreciate some advice please....

There are four wires coming from the Motoplat alternator - two yellow, one red and one blue (which is cut off and goes nowhere). The two yellow and one red go to the regulator/rectifier - does it matter which way round the two yellow wires go, as long as it is to the two yellow terminals? The reason why I ask is that the insulation of the wires has hardened and is flaking off next to the R/R, and where the wires exit the crankcase. Strangely they seem ok inside the engine.

What can I do about the wires? I cannot fit new ones because they are encapsulated in the alternator stator, so should I try to fit heat shrink over them? This may make the loom too big to fit through the rubber sealing grommets. Or should I cut them near to the stator and solder new lengths of wire in? This may be problematical, as I have never managed to solder wire to wire......

Cheers,

Colin

[mrkprsn]

Colin,

I've been having the same problem you are. My alt wires outside the case have deteriorated. They now have to be replaced since I lost power from one of the wires. I just bought some 2 core wire to accomplish this. You would need a three core wire.

I measured the OD of the Alt wire and it was 8mm. This wire I bought has an OD of 7.5mm so that's close. I previously bought Ducati NC replacement stator wires that were just two yellow 16 gauge wires without the correct OD size so I won't be using those. I bought this. https://www.amazon.com/dp/B0BKH19XP8?re ... tails&th=1

If your wire is OK inside the case you may be able to put heat shrink on each wire that's outside the case. After that I would put one more layer of heat shrink over all the wires and run it like that. I would not cut the wires inside the case. If you are going to do that I would instead desolder the wire(s) from the alternator and solder in a new wire(s).

Good luck, Mark

[Duccout]

Thanks Mark,

It does not appear possible for me to solder in new wires as they just disappear into the encapsulation of the stator. I think that heat shrink may be the best idea, as it is sort of fool proof!

Colin

[Jon Pegler]

Hi Colin,

If you've got two yellow, a red and a blue wire you have got one of the Motoplat alternators for use with electronic ignition, which was not an original fitment to a Strada.
The severed blue wire was the direct link to the electronic ignition coil.
You can use the two yellow wires on either side of the regulator.
If you cannot attach new wires, Bradford Ignitions in Cornwall will be able to deal with the encapsulated stator coils and fit new wires.

Jon

[Duccout]

Hi Jon,

Thank you, very useful, I wondered why there was an extra wire. Thanks for the info about Bradford Ignitions, I'll keep it in mind.

Cheers,

Colin

[themoudie]

Aye Colin,

The '75 350 MKIII widecase undergoing surgery at present had the Motoplat alternator fitted and the cables on leaving the encapsulated stator had crumbling insulation, not only within the crankcase, but also outwith. As the engine was missing the Motoplat ignition trigger etc and the rectifier also didn't appear to healthy along with the rest of the "multi coloured spaghetti" (cracked insulation, verdegree below the insulation and blackening of the copper cables inside) recycling the whole assembly was my option. Degrading, 45 year old plus electrical components aren't worth the hassle and Electrex replacements along with a new homemade loom are going to be the order of the day. However, I wish you well with the heat shrink.

Thanks to Jon, for drawing my attention to Bradford Ignitions, I will see if he can sort out something for my Morini 125H. Nobody else has come close, so far, and I am convinced that the trigger coil is to blame.

Good health, Bill

[Duccout]

Hi Bill,

I had a look at the Bradford Ignitions website and it looks like they can do almost anything, so there is hope for the Morini.

Hope all is going well with your rebuild!

Cheers,

Colin

[Ventodue]

If you've got two yellow, a red and a blue wire you have got one of the Motoplat alternators for use with electronic ignition, which was not an original fitment to a Strada. The severed blue wire was the direct link to the electronic ignition coil. <snip>

JFI Colin, here's the wiring diagram for the set up Jon is talking about ...

Motoplat.jpg

[Ventodue]

<snip> ... the insulation of the wires has hardened and is flaking off next to the R/R, and where the wires exit the crankcase. Strangely they seem ok inside the engine.

Happens on the twins too, Colin. I guess it's down to the heat generated at/by the reg/rec, probably (?)due to corrosion of the connectors.

Was a certain Mr. Brancato who put me on to that, many years ago now.

[Duccout]

Hi Craig,

Thanks for the diagram, I wonder why the bike had the original alternator changed? Burnt out most probably. Whoever did the change was professional, because they used a new tab washer on the crankshaft nut and obviously had a proper flywheel extractor. If only old bikes could talk, what a story they could tell - my Strada is 46 years old and has not done many miles because the gearbox looks new and it is on the original piston; I know that at sometime the top bevel bearing broke up, so I am guessing that this resulted in the bike being laid up for a long time, before being butchered back into life.

A browse through the Ducatis for sale on Milanuncios shows a lot of Stradas and Forzas (particularly Forzas) that have been off the road for a long time, probably as a result of a 'mishap'.

Cheers,

Colin