Stornello charging issue

Hi all
I have a 61 Stornello 125 Turismo, it runs fine and lights work ok but the battery doesn’t charge.
I’ve traced the problem to the diode on the connector board in the headlight unit. A new diode from a electronics firm on eBay fitted but failed as soon as the bike was started, presumably because it wasn’t the correct amperage.
Does anyone have any idea if something suitable is available? Or what capacity / rating it should be.


Hello Dennis, please can you post a photo of the original item? Does it have any markings or numbers on it?

Best wishes Chris

Looking at the diagram, 1960_Stornello_125 fuse is 15A so I might make the diode equal to that. At least 10 Amps (it seems to be a 30W total system). Another limiting factor for the diode is maximum reverse Voltage, I’d want at least 50V. 100V would be even better. Because it’s half-wave rectified, the reverse Voltage has no load on it, so can be whatever it wants to be.

Thanks for the replies. Unfortunately there’s no markings on the original diode. I’ll try the local auto electric and see if they can help. If that’s no good at least now I have a better idea of what voltage I should be looking for.

Hi Dennis I have a 1965 Stornello Turismo. Your diode looks the same as mine, as you say it is a basic half wave rectifier. The top coil on the stator has 2 windings, one for lights and one for battery charging. The headlight is AC, the horn, stop light and parking lights are off the battery.
I must admit, I plugged mine in and it just worked. This is the wiring diagram I followed. .

Hi Don
The diode on yours looks very much the same as mine but mounting board looks a bit different. I’m fairly sure the wrings is as your diagram but I can’t find a Bobina impedenza [I presumen thats a resistor].
I’m going to take the diode to the local auto electrical shop when I get a chance, he seems confident he’ll be able to find something.

That board is a bit different to mine. Do you have a wire coming from the bottom of the Diode heading off to the battery +ve?
I dont think mine has the bobbine impedenza unless it is buried inside the ignition switch.

It translates as “Impedance coil” so yes it is a resistor but in an AC circuit. Impedance is the superset of both resistance and reactance combined. Where reactance is the measure of the opposition of inductance and capacitance to current in an AC circuit.

I agree ask at your local auto electric expert.

Switch is different as well, according to the wiring diagram they used cev and aprillia components maybe that’s the difference?
The wire off bottom of the diode does go to battery + the other side goes to the light switch

That is very different, as you say they used a few different sppliers. This is likely to be your wiring diagram but the basic principal of the charging circuit is likely to be the same.
Thinking back, the headligt on mine came from a Stornello sport that was broken for spares about 8 years ago, hence the difference.

Eventually got a diode, its not the same type as original just a standard looking in-line diode.
soldered in ok and I’m getting 7v at the battery when I rev it so happy with that. I will keep looking for an original type one but at least I’ve confirmed what the fault was.


Hiya Dennis Just waking up an old thread. I have just finished the rebuild of a 1966 Stornello and when I started the bike up, the headight was barely glowing. A bit of investigation and both the lighting and charging circuits were only putting out 4 volts max.
I sent the coil off to West Country Windings in Thetford and they are rewinding it as a single winding (Currently it has 2 windings on a single centre and uses the frame as part of the circuit) The new single winding will feed into solid state rectifier / regulator and feed all its power into the battery.
I will then feed battery power into the lighting circuit instead of the standard AC lights. Hopefully I will be able to see at night once it is all connected up.
This upgrade does away with the single diode half wave rectifier if you are still having problems,

1 Like

That sounds like a good idea Don. Mine is working ok but the lights are pretty much useless as they almost go out when you slow down, can make for a interesting journey. Would be interested to see how it works out.

1 Like

The obvious answer is “don’t slow down” lol. Cheers Phil

The rewound coil arrived from West Country windings today and was quickly inserted into the engine. Amazing service from this company, I sent it to them Tuesday, they phoned Wednesday to say they had received it and it would be done next day. They sent it Thursday and I received it on Friday. Total cost £60.
A quick test showed it easily produces up to 20V AC and when conected to what is supposed to be a rectifier / regulator, it produced 20V DC. That’s what you get for buying cheap chinese parts off ebay! It should be regulating it to 6V, but it is obviously just a rectifier.
I have ordered a proper 12V rectifier / regulator and a new 12V battery and will see how that performs.


Well, I have assembled eveything and started it up and all is looking fantastic. I have used a Lucas 12v rectifier regulator mounted under the seat. That connects to the 2 yellow wires from the newly rewound coil output wires. The other pair of r/r wires go to the battery +ve and -ve terminals.
I have added an extra battery feed into the terminal board in the headlight to replace what would have been the AC input on the board with 12v so the headlight is now fed with battery power. I’m getting around 14Volts on the battery and a nice new LED headlight bulb is looking very bright. If you go down this route, don’t forget to change the rear light bulb for a 12 volt one.
The 6 volt rated horn is also very LOUD!!
Once I get the bike registered, I will try it out on the road.

1 Like