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I have also posted this in the projects section as a follow up the Sasche Ignition I have fitted to my 500W.

I need some help understanding the electrical connections of the stator.

Last night I connected a used 12V stator that was removed from a 3-1/2 (no white ground wire) and worked on tuning the bike, after I was done the ignition key was turned off. This morning there was a distinct electrical smell in the shop and the right hand engine cover was warm and a strong electrical burning smell from inside the cover. Removing the right hand cover the five charging coils were dark brown and stains of cooked varnish were on the cam pulley and the inside of the rotor. Looks like the stator charging coils have shorted out. I don't know why or how electricity got past the key switch to burn out the coils when the key was off.

With the Sasche ignition the system is converted to battery / coil ignition, the ignition coil (one of the six) mounted to the fixed body of the stator is no longer used, the GREEN wire coming from the ignition coil and out of the wire bundle from the stator is no longer used and is therefore disconnected from the fuse box. That leaves the five charging coils active to recharge the battery, a fully charged battery is essential for battery / coil ignition. There are two YELLOW wires coming from the stator that connect to the voltage regulator.

There is a RED wire that comes from the stator wire bundle that connects to the fuse box. This RED wire connection plugging in to the fuse box is located at a pair of joined lugs (four lugs in total) that are HOT from the battery], always powered from the battery to the stator. I don't understand why the charging coils have a HOT red wire direct to the stator.

MY FIRST QUESTION

If I am only using the stator for the battery charging function can I leave the RED wire from the stator disconnected at the fuse box and only leave the two yellow wires connected to the voltage regulator???

MY SECOND QUESTION - Voltage regulator connections

The voltage regulator I am using is the early type used on the 350, It has markings beside the lugs that are labeled BROWN / RED / YELLOW / YELLOW. The edge of the cast aluminum body beside a mounting hole is stamped GROUND (earth). If I have things right, the two YELLOW wires from the stator plug into the voltage regulator lugs marked YELLOW. I take it the YELLOW wires are the AC generated current from the stator to the regulator.
I have connected a BROWN wire from the fuse box 1st lower lug on bottom left of fuse box, to the BROWN lug on the voltage regulator. I take it this BROWN wire is feeding DC current into the fused circuit BROWN that is shared with the BROWN from the ignition switch. When the engine is running the DC current from the regulator is charging up the battery.

A ground (earth) wire is connected from the securing bolt on the voltage regulator body to a ground (earth) connection on the frame.

There remains a lug on the voltage regulator labeled RED. I don't see any indication on a wiring diagram that uses this RED lug. Am I correct that the voltage regulator RED lug is not used. ?

Thanks for any help, I am trying to find out if I caused the stator to fry or if was already shorted out before I installed it.

Hi,
That's very annoying.

There is a RED wire that comes from the stator wire bundle that connects to the fuse box. This RED wire connection plugging in to the fuse box is located at a pair of joined lugs (four lugs in total) that are HOT from the battery], always powered from the battery to the stator. I don't understand why the charging coils have a HOT red wire direct to the stator.

This is a very conventional system used on many Italian motorcycles (Ducati, Morini) and scooters (vespa) . The red wire is a centre tap of a winding that connects from yellow to yellow.
On some vehicles there may be a fuse in the red wire connection to the battery (Morini 250-2C for example) . It was in 1970s/1980s cheaper regulator than a 2 wire Bridge/switched bridge rectifier/regulator.

A certain fault in the regulator where one or both of the thyristors between yellow and ground is conducting permanently will cause the battery to discharge through the stator winding.
Battery -> RED -> YELLOW -> thyristor -> Ground. There is no protection against this.

Another fault could be that the stator had a short between any of the red or yellows to the stator plate (earth) via a number of coils.
Many times people omit to check the measurements from all the red,yellow connection to ground, with stator leads disconnected, but with the stator fitted.

If I am only using the stator for the battery charging function can I leave the RED wire from the stator disconnected at the fuse box and only leave the two yellow wires connected to the voltage regulator???

No
The red stator wire has to connect to the battery if you have a three wire regulator which was standard on a 350, which matches your description . The charging circuit will not function without it. The red or B+ connection on the regulator has NO INTERNAL connection to the regulator, it is used as a hookup for machines that do not have a fusebox
and have just a simple in line fuse.
So in your case you connect the RED stator wire to the fuse box and connect the fusebox to the battery and the ignition switch.

The voltage regulator I am using is the early type used on the 350, It has markings beside the lugs that are labeled BROWN / RED / YELLOW / YELLOW. The edge of the cast aluminum body beside a mounting hole is stamped GROUND (earth). If I have things right, the two YELLOW wires from the stator plug into the voltage regulator lugs marked YELLOW. I take it the YELLOW wires are the AC generated current from the stator to the regulator.

Yes - but how do you know its an early 350 type, there should be a part number on it somewhere, the 500W had a different 2 wire regulator except the very first produced.

There remains a lug on the voltage regulator labeled RED. I don't see any indication on a wiring diagram that uses this RED lug. Am I correct that the voltage regulator RED lug is not used. ?

As above its only used for machines that don't have a fusebox.
A fuse in line would not actually prevent battery discharge, it would protect a red to earth direct short.

Thanks for any help, I am trying to find out if I caused the stator to fry or if was already shorted out before I installed it.

So possible faults
1. internal short in stator red to ground via some coils somewhere.
2. regulator fault - thyristor short to ground.
This can be readily checked by measuring Yellow terminal to ground (regulator case) resistance (you may need to check on diode setting)
3. Fusebox fault - in this case severe heat damage in the fusebox would be obvious.

One thing to be aware of is that a discharging battery through the lighting coils can cause de-magetisation of the rotor.

Hope that helps.
Unfortunately the stator will need to be rewound.
I recommend that you should replace the ancient regulator with a two wire modern equivalent (and the proper type for a 500W)
I can explain how it needs to be wired later.
I also recommend that you put a transient voltage suppressor TVS diode to protect the Sachse system from the vagaries of dodgy charging systems.

In the case of rapid battery disconnection in Ducati regulators a nasty effect called a transient load dump can occur,
meaning that there can be large voltage spikes, which can destroy electronics or blow up the regulator. Some Ducati regulators have a red warning label about this.
"Do not disconnect battery with engine running"
Mark

Thank you Mark!!

fantastic information.

Would this regulator work? I just used this one to upgrade a 1975 Ducati 869 GT



https://store.bevelheaven.com/Electrica ... Drive-etc/

The rotor has decent magnetic strength, I do have a spare that I could send to the UK to get re-magnetized just to be certain.

I don't see any heat damage on the fuse box but the charging coils are definitely baked.

Any information on wiring up the regulator is very much appreciated!

Hi,
according to their site:
This will fit ALL Ducati bikes with single phase, 2-wire generator. Specifically, all bevel drive twins including; 750GT/Sport/SS, 860GT/GTS, 900SS, Darmah. Also fits; 1989-93 906 Paso/907IE paso, 1986+ 750 F1/Sport/Paso, 1990-93 851/888, 1994-97 916, all years PANTAH, all years bevel drive, 1997 only 748, 1992-97 M900 Monster, + many other applications..... Comes with wire diagram and mounting / installation instructions for both 2 wire and 3 wire applications.

Yes. And you should wire as a two wire. Leave the red wire from the stator unconnected. Tape it up ensure it doesn't touch anything and label DO NOT CONNECT. If you are having the stator rewound you could omit it altogether. However my experience over many years of wiring shops [automotive, aircraft, telecomms] is any thing other than please rewire exactly as is, just confuses them.
It looks like there are two red wires connected together from the regulator this goes to the fuse box (and battery and switch),you could have two spade terminals .The remaining two black and white, you should double check the wiring instructions, one might well be 12V switched supply (was brown on Morini) - the other is either a charge indicator or an earth, I don't know.

Its a bit inconvenient for you that it comes with bullet connectors, but I guess you will be able to sort that out.

Mark

mbmm350s wrote:Hi,
according to their site:
This will fit ALL Ducati bikes with single phase, 2-wire generator. Specifically, all bevel drive twins including; 750GT/Sport/SS, 860GT/GTS, 900SS, Darmah. Also fits; 1989-93 906 Paso/907IE paso, 1986+ 750 F1/Sport/Paso, 1990-93 851/888, 1994-97 916, all years PANTAH, all years bevel drive, 1997 only 748, 1992-97 M900 Monster, + many other applications..... Comes with wire diagram and mounting / installation instructions for both 2 wire and 3 wire applications.

Yes. And you should wire as a two wire. Leave the red wire from the stator unconnected. Tape it up ensure it doesn't touch anything and label DO NOT CONNECT. If you are having the stator rewound you could omit it altogether. However my experience over many years of wiring shops [automotive, aircraft, telecomms] is any thing other than please rewire exactly as is, just confuses them.
It looks like there are two red wires connected together from the regulator this goes to the fuse box (and battery and switch),you could have two spade terminals .The remaining two black and white, you should double check the wiring instructions, one might well be 12V switched supply (was brown on Morini) - the other is either a charge indicator or an earth, I don't know.

Its a bit inconvenient for you that it comes with bullet connectors, but I guess you will be able to sort that out.

Mark

Thanks again Mark !!, fantastic help,

I have gone ahead and ordered the new regulator and will check their instructions for the two wire installation to your notes. Hopefully this solves the ignition and charging once and for all.

I will let you know how I make out when the new reg arrives.

Cheers

Jim