Stornello 160 electrical system

[osvaldo]

Hi everybody,

first of all excuse me for my English, I know it is not so good...

I have got an old good 1974 Stornello that is giving me trouble with the electric circuit.
It has been modified by the previous owner eliminating the battery and changing some connection on main switch.
In my opinion it can be used in daylight only cause the light are... let say...funny.

So I want to get back to the original but first i would like to fully understand the logic of the original circuit.
If I look at the original schematic (see picture) I get a bit confused mainly because is missing the internal schematic of the magneto and I can't really imagine how the switch is suppose to change connections in every position.





So I found in the net another schematic that is a title bit easier as far to imagine how main switch work even is rappresented separate in item 2 and 19 while in realty is in one block only.







 
I am reasoning on these and I will appreciate a lot if some kind guys follow me and tell where I am wrong:

So Item 19, quite simple, pushing down the key, from off to on, disconnect from the ground the gray generator cable from the ignition coil enabling spark.
In the mean time connect the negative pole of the battery to the frame (ground).
Horn and stop light are enabled if you push their switch.
Is that correct?
Now let see item 2.
I know that green and red cables from generator come from two different point of the same coil, giving different voltage; let say around 3.000 rpm 16 V the green and 8 V the red.
With key on, centre position engine running, green charge the battery trough blue passing a diode.
Since current from the diode is just half wave 16V AC seems to be more or less correct for the task of charging a 6V battery.
Same if you turn key to the right.
I suppose upper part of the rotor in the main switch turn together with the lower and is always connected with the yellow cable.
If so, turning key to right we light trough black and yellow cable, front and rear city light plus instrument if there are.
If we turn key to the left we switch off front city light ad send current to hi/low beam, depending on the position of external switch.
Up to now am I correct?
But what about battery? If we pass trough a single diode an 8V AC are we going to have enough voltage to charge the battery?
Plus in the previous case current come from fuse trough black cable and can be aided from battery, while in this case it come from generator trough red cable.
It can just go to the battery, if its voltage is high enough, but not get back due the diode.
The hi/low light are totally dependent on alternator and going up and down with engine RPM.
Now the questions:
It is supposed to be like this?

I will be tankful to everybody would be so kind to give me his opinion.

Ciao
Osvaldo

[Canuck750]

I think what you are describing is correct, my 1972 Benelli 175 Enduro uses a similar system, simple CEV pin key, depress for ignition / brake light, turn key to left for lights, to right for park lights. The headlight shell contains all the electrics.



the CEV stator has an ignition coil and a lighting coil, if its like other small displacement CEV magneto ignition the ignition coil also feeds the brake light.



Gilera 106 SS uses similar CEV unit but has no battery, grey wire to 6V coil + terminal, green to rear brake light stop switch, red to lights

[osvaldo]

Hi,
thank you for your answer.
Yes, your Benelli schematic look to be very similar to my Storello, apart of the resistor added to the charging sistem.
Even the main switch is as difficult for me to undestand, as the original from Moto Guzzi.
One difference is that mine has only one coil for light from which are coming out red and green used the first for hi/low beam in AC and the second in DC for stop, horn and effective battery charging.



I am quite convinced that red cable can not be useful to charge battery.
I am also sure that if they done it like this must be for a reason.
Just to be, that I am like a newby with this problem, seems to be a bad way to supply current to the bike.
Where am I wrong?

Ciao
Osvaldo

[Howard R]

You do correctly describe the operation of the electrical system, the yellow wire goes to rear & instrument lights through the bridging terminal on the top half of switch #2.  The bottom half of switch #2 controls battery charging, top half controls lighting.  The blue wire through the diode is the charge to the battery, and is jumped to two positions on the switch.  The green and red are AC from the magneto, it might help to think of them as red = high current (6 amps?) and green = low current (3 amps?), not necessarily as different voltage taps.  (As you say, without seeing how the magneto AC coil is wound, we really can't say what the AC voltages are.  Since everything is designed around 6 volt battery & light bulbs, I think the difference between red & green is more likely current instead of voltage.)  As shown, the green is connected to the blue to charge the battery, and all lights are off.  In City position, green is still connected to blue to charge the battery, and fused hot from the battery is connected to the city, rear, and instrument bulbs.  With the switch in Headlight position, AC is fed to the headlight through high/low selector and red is now connected to blue to charge the battery.  Horn & stop light are high current draw but intermittent/low duty controlled by their switches, with fused hot from the battery providing current for the extra load.

Howard

[osvaldo]

Hi Howard,
thanks for your reply, and excuse me for the delay to answer.
I was busy discussing on an Italian forum with one guy that in my opinion is very strong on electrical matter.
We get to the conclusion that red and green supply different voltage as they are connected in the middle and at the end of the coil.
Just the cable are almost new, so they have been replaced and very probably inverted in position.
If you keep in mind this the schematic make a bit more sense even if I can't say is the most bellyful.

Thanks a lot
Osvaldo