G15 magneto kill switch

Hi Knut,
thank you so much.
I have placed to day a new "06.8061 MAIN HARNESS BRAIDED (ATLAS/650) 54939968 WITH MAGNETO” that seems almost the same for G15.
Three questions, please:
1. the white wire from mag goes from kill switch to ground?;
2. can i add a capacitor?;
3. the harness has three wires from alternator (GB, WG, GY). Only GB and WG go to the rectifier while GY goes directly to the litning switch. I dont have a three wires old alternator but only a later two wires WG and GY. Can i join GB with or WG or GY?.
Thank you.
Piero
 
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The white wire goes from the K2F magneto to the kill switch. When the switch is pressed, the white wire is connected to ground.

No capacitor is needed if your magneto is in good condition. Regardless, adding a capacitor to the white wire is not the proper place in the circuit.

I recommend you use a modern rectifier/regulator such as a Podtronics. With a 2 wire stator replacing a 3 wire, you risk over-charging the battery when running with main beam light off.

With a modern rectifier/regulator, connect GY from the stator to one of the yellow wires on the rectifier/regulator, and connect the WG on the stator to the other yellow wire on the rect/reg. The GY to the lighting switch becomes unused.

I hope this is clear.

Slick
 
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texasSlick said:
With
Click to expand...
Hi Slick.
About capacitor, i meant to add it on NU and ground.
You say “ The GY to the lighting switch becomes unused.”.
But on the rectifier (from the alternator) dont arrive GY but GB.
If i use a Podtronics (i have it with capacitor in) can i use GB?
In any case, was the original stator the LU47204 RM19 single phase 3 wires?
Was it a 6 or 12 V?
Please let me understand better.
Thanks.
Piero
 
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The original stator was LU 47164A. LU 47204A was a replacement.
The description of the latter says "stator, RM19, 3 wire, 6V".
12V is obtained by combining alternator coils in the 88SA switch, according to my understanding. Maybe someone can jog my memory and explain the physics how two parallel coil groups (each group consisting of 2 coils) will generate 12V rather than 6V.

It should be noted that on early coil ignition models (e.g., 1964 model G12), the charging system is semi-12V, because one stator coil still drives the two 6V coils directly. Lucas names it a "12V two charge rate".

Lucas service manual SB519 contains a wealth of information and I think diagrams are clearer as in the workshop manual. However, please have a look in the AMC workshop manual page 107-108 as well.

-Knut
 
You have jogged my memory as the very first Lucas alternator I think was a RM19, and yes Lucas DID come out with a 3 /4 page sheet on how to convert it to 12 volts back in the 1960s
 
Hi All.
Sorry, but 1964 G15, line wiring diagram, had a 12 V system with rectifier and
zener diod, magneto.
My new harness, from a 1964 Atlas, has thre wires from alternator, two to rectifier (GB and WG) and one GY to lightning switch.
I must use the 6 V lucas three wires stator,
ir use the 12 V stator and join GB with GY like 1969 BSA Rocket 3?.
Please, the question is if the 1964 G15 wiring was a 12 V what is the stator to use?
Thank you
Piero
 
mdt-son said:
The original stator was LU 47164A. LU 47204A was a replacement.
The description of the latter says "stator, RM19, 3 wire, 6V".
12V is obtained by combining alternator coils in the 88SA switch, according to my understanding. Maybe someone can jog my memory and explain the physics how two parallel coil groups (each group consisting of 2 coils) will generate 12V rather than 6V.

It should be noted that on early coil ignition models (e.g., 1964 model G12), the charging system is semi-12V, because one stator coil still drives the two 6V coils directly. Lucas names it a "12V two charge rate".

Lucas service manual SB519 contains a wealth of information and I think diagrams are clearer as in the workshop manual. However, please have a look in the AMC workshop manual page 107-108 as well.

-Knut
Click to expand...
Hi Knut.
But the 1964 G15 had the magneto not the coils.
What i must do?
Piero
 
Piero:

Here is the way I connected a 2 wire stator to a Podtronics regulator on my Atlas:

Like yours, my stator wires are WG and GY.

Connect WG (stator) to WG (harness) to Y (Podtronics)
Connect GY (stator) to GB (harness) to other Y (Podtronics)

The GY (harness) to light switch is unused.
The GB (light switch) to rectifier is unused.

RE: Capacitor at NU wire: The voltage of the NU wire is rectified DC. A capacitor connected here will reduce "ripple" to produce a smoother dc waveform. It is not necessary if you are using a battery. There may be some benefit without a battery.

All:

The voltage of a coil in a rotating magnetic field is a function of the number of turns of wire on the coil, the magnetic flux (strength of the magnet), and the rpm of the magnet. The voltage is AC and is not limited by anything .... as much as several hundred volts can be obtained in an open circuit. This can be easily measured .... disconnect both stator wires from the bike's harness, connect a VOM on the open wires (AC scale on meter), and rev up the engine. Thus, there is no such thing as a 6 v. or 12 v. stator .... it is the Zener diode, or a modern rectifier/regulator, that sets the voltage.

The 3 wire stators were intended to be used to match the stator's power output to the lighting load. This was before the advent of Zener diodes. Refer to the sketch below:

G15 magneto kill switch

The six coils of the stator are wired in three pairs as above.

For LOW output, wires GB and WG are connected to the rectifier.
For MEDIUM output, wires GY and WG are connected to the rectifier.
For HIGH output, wires GB and GY are joined together and with WG are connected to the rectifier.

The lighting switch makes the necessary connections to match output to load.

NOTE: The description above is simplified for easy understanding. Those who understand the physics might argue with this, but I think a technically correct version will muddy the water.

The 2 wire stators simply connect the GY and GB wires internally to the stator and bring out only the WG and GY leads. With a 2 wire stator, the power output is all or nothing, and load matching cannot be done. Thus, the load matching function of the lighting switch becomes unnecessary, or superfluous. For this reason, a 2 wire stator must have a Zener or modern regulator to prevent over charging the battery.

HTH,

Slick
 
pierodn said:
Hi Knut.
But the 1964 G15 had the magneto not the coils.
What i must do?
Click to expand...

Simple. Look up the wiring diagram in the 1964 workshop manual, p. 107-108. There is a diagram for magneto-equipped bikes (G15) and one for coil-equipped models (G12 Roadsters, also applicable to 1968-69 G15's). Connect wiring as shown using the genuine parts (rectifier, zener, switches). Then it should work.

pierodn said:
Please, the question is if the 1964 G15 wiring was a 12 V what is the stator to use?
Click to expand...

LU 47204A. The stator operates in 6V as well as 12V mode.

Good luck!

-Knut
 
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Hello well you could do as I have and taken the white wire to a on off key switch off going to earth fitted in the tool tray and poking out under the side of the seat so you can get your key in and then a wire to the handlebar next to the throttle as emergency cut out but the choices is your its your bike,
 
Hi.
Please, another help with wiring harness.
From the harness arrives into the head lamp shell the wire U (blu).
The wiring diagram says to join this U wire to the U from dipper switch and then to UW for dip beam and UR for main beam.
My dipper switch has:
1. NB for push the horn;
2.U;
3.R;
4.W.
Please, where i must join the UW and UR from lamp?
Or my dipper switch is not correct.
Thank you for helping me.
Piero
 
Last edited:
pierodn said:
Hi.
Please, another help with wiring harness.
From the harness arrives into the head lamp shell the wire U (blu).
The wiring diagram says to join this U wire to the U from dipper switch and then to UW for dip beam and UR for main beam.
My dipper switch has:
1. NB for push the horn;
2.U;
3.R;
4.W.
Please, where i must join the UW and UR from lamp?
Or my dipper switch is not correct.
Thank you for helping me.
Piero
Click to expand...
Think you have an Emgo reproduction switch with non Lucas wire colors. Maybe this is helpful https://www.classicbritishspares.com/blogs/news/lucas-31563-handlebar-switch-wiring
 

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