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Motoplat 12v AC Stator Conversion How-To Redux

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Most well versed Serveterans are already aware of the 12v AC conversion using the original Motoplat stator.  This conversion results in some of the most powerful lights I have ever seen on a Lambretta.  If you ride a Spaniard and haven't done this conversion, you are missing out.


I'm currently building a fellow LCUSA clubmate's LI150 and while we are waiting for all the fun stuff from Adam @ Soulpower scooters, I thought I'd revisit this conversion and take it a step further.  I had already set him up with this conversion when we put his scooter on the road a few years back but he knows I like to mess around in the shop when I'm bored so he told me to clean up the ugly Serveta wiring if I feel like it.  Well I had a minute today and took a look at the stator and decided to simplify the wiring starting here and moving to the harness later.


The 12v ac conversion is basically:

-ground 1 yellow wire from stator

-plug other yellow wire from the stator into the power wire of an AC regulator

-Tie off the red wire from the stator as it's no longer needed.


So to take this a step further, I figured I'd:

-ground 1 yellow wire to stator base

-remove red wire from stator

-add black ground wire to stator to avoid confusion later


The Motoplat stator does not feature a ground pole on the steel laminations as found on electronic ignition stators so I didn't have something to tie the yellow wire to.  The first step was to make a ground pole:


On the winding to the right of the yellow wires is a nice open space to add a pole.  Center punch a spot around the middle of that area:




Then get out the drill!  I chose an m4-.70 screw from my junk bin to use as a pole so I needed to drill it to 1/8" for the tap.  I don't have bottoming taps so I needed to drill it a little extra deep to get the amount of threads I needed for the scew:




Tap it to the size of the screw you intend to use:




Now we have a ground pole on the stator laminations:




From there, I wanted to switch the side of the winding that the yellow ground wire will feed from so it has a direct route to the ground pole. It doesn't matter which yellow wire you choose to ground, just as long as you ground one of them.  Heat up the soldering iron and melt the solder in the grommet until you can yank the wire out.  




Switch it to the other side and solder it in place.  I should note I have never considered myself a master solderer but I do think I'm starting to finally get better and this was good practice.




Now heat the solder up in the red wire's grommet and remove the red wire:




Now add some eyelets to the yellow stator ground wire and the new black ground wire I will be adding to the stator harness.  Solder those joints to ensure great connections and tie them to the fresh new ground pole you added:




Route the black wire and feed it through the stator harness sleeve.  Add a zip tie for a clean installation and enjoy your new 3 wire 12v AC Motoplat stator with super bright lights:




New configuration:


Yellow = Lights: attach to ac regulator

Green = Spark: attach to ignition coil

Black = Ground: attach to bare metal frame ground

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I should note that adding the ground pole was completely unnecessary as one of the yellow wires acts as a ground anyway. The only reasons I chose to do it is because:

-I could

-having 2 yellow wires is confusing when you are working on the scooter.

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To simplify this even more, I'm going to switch out the remaining yellow wires for a red.

That way when you go to plug it into the harness, your not confused about having a yellow and a red plugged into the positive poles of the regulator. They will both be red, which will avoid later confusion.

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