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@sdjohn avatar
UTC

Veni, Vidi, Posti
'15 GTS300, '86 PX125EFL, '66 VBB, '01 ET4
Joined: UTC
Posts: 8248
Location: San Diego, CA
 
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@sdjohn avatar
'15 GTS300, '86 PX125EFL, '66 VBB, '01 ET4
Joined: UTC
Posts: 8248
Location: San Diego, CA
UTC quote
OK so maybe you have something that looks like this, but isn't lighting your lights any more:
External inline image provided by member with no explanatory textVespa 12v AC conversion by john.headley, on Flickr

You can easily switch this to 12V AC, have brighter lights, and stop worrying about battery maintenance.

First, remove the battery.
External inline image provided by member with no explanatory textVespa 12v AC conversion by john.headley, on Flickr

Get rid of the useless regulator/rectifier that was the reason your 6V battery wasn't charging.

External inline image provided by member with no explanatory textVespa 12v AC conversion by john.headley, on Flickr

Open up your headset and ditch the "sealed beam" 6V headlamp that doesn't have a replaceable bulb. Swap your connector ends with regular spade terminals for the replacement bulb housing.
External inline image provided by member with no explanatory textVespa 12v AC conversion by john.headley, on Flickr

Install the new bulb style headlamp, swap out your 6V high beam and speedo bulbs if you want. I ordered the wrong style, so I let it ride and they didn't blow later when I tested it, so I think they might live.

External inline image provided by member with no explanatory textVespa 12v AC conversion by john.headley, on Flickr

Swap your brake light for a 12V version:
External inline image provided by member with no explanatory textVespa 12v AC conversion by john.headley, on Flickr

Mount up a 3 pole 12V PX style regulator, the hole pattern is the same so it's no sweat. Make yourself a ground lead for the black pole on the regulator.

External inline image provided by member with no explanatory textVespa 12v AC conversion by john.headley, on Flickr

Shrink wrap the ends of the white that feeds the turn signals and the white from the stator.
External inline image provided by member with no explanatory textVespa 12v AC conversion by john.headley, on Flickr

I decided to use a 12V DC Lambretta junction block to mate the power and loom leads. If you buy the DC version, all of the terminals except the green pair are electrically connected, so you can just plug in your regulator connection to one and the loom leads for the headlamp and brakelamp circuits anywhere else (except the greens, of course). Take one of the yellow stator wires and give it a loop and ground it on the regulator, along with your ground pigtail you created and with the loom ground. The other yellow goes to your new regulator. Make a yellow lead to connect the regulator output to the junction block. Tuck the red wires back into the loom sleeve to keep it neat.

External inline image provided by member with no explanatory textVespa 12v AC conversion by john.headley, on Flickr

Shrink wrap the white ends and the extra ground terminal. Tie it all back neatly and tuck it out of the way.

External inline image provided by member with no explanatory textVespa 12v AC conversion by john.headley, on Flickr

Now you are ready to rock bright 12V lights. If you want, order a 6V AC horn to complete the conversion. There is no 12V AC horn but the SIP catalog says the 6V will do fine. I ordered one but mine hasn't yet arrived.

Want to make this conversion easier? Buy all of the bullet connectors (3.5mm), spade connectors (F63 and F63S sleeve), and a Professional Kit CK-1 which includes a quality crimping tool from vintageconnections.com. He ships fast and the stuff he sells is good quality.
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@sdjohn avatar
UTC

Veni, Vidi, Posti
'15 GTS300, '86 PX125EFL, '66 VBB, '01 ET4
Joined: UTC
Posts: 8248
Location: San Diego, CA
 
Veni, Vidi, Posti
@sdjohn avatar
'15 GTS300, '86 PX125EFL, '66 VBB, '01 ET4
Joined: UTC
Posts: 8248
Location: San Diego, CA
UTC quote
By the way if you want to keep your signals, there is a 12V AC Bajaj flasher out there that will do the job in place of the existing one. You might find the stator can't put out enough for the lights and signals at idle with a brake light on. If this happens to you, you can replace 2 of the 4 bulbs with LED bulbs and it should do the trick. I did this on my old Lambretta.
@mrj avatar
UTC

Addicted
ET3
Joined: UTC
Posts: 569
Location: OC
 
Addicted
@mrj avatar
ET3
Joined: UTC
Posts: 569
Location: OC
UTC quote
Nice one sdjohn! Tidy wiring and bye bye battery. Thumbs up brother.
@v_oodoo avatar
UTC

Style Maven
'74 50s x3 '87 PK125XL '92 PK50XLS Plurimatic - & - '58 AllState '68 Sprint '66(?) Super125 and '72 DanMotor Super150
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Location: seattle/athens
 
Style Maven
@v_oodoo avatar
'74 50s x3 '87 PK125XL '92 PK50XLS Plurimatic - & - '58 AllState '68 Sprint '66(?) Super125 and '72 DanMotor Super150
Joined: UTC
Posts: 9541
Location: seattle/athens
UTC quote
I can't be sure, but that seems electrically very similar to the way I found and posted here on page 5
https://modernvespa.com/forum/post1753966#1753966 , it seems that having the two yellow stator leads is the key.

I do like the idea that you can use the Vespa regulator. Here's the linked setup on a friends V90.
The regulator is to be moved to upper left corner to fit a small tool case.
External inline image provided by member with no explanatory text
test wired

External inline image provided by member with no explanatory text
connections wrapped & tucked in, big washer is reliable ground for testing
OP
@sdjohn avatar
UTC

Veni, Vidi, Posti
'15 GTS300, '86 PX125EFL, '66 VBB, '01 ET4
Joined: UTC
Posts: 8248
Location: San Diego, CA
 
Veni, Vidi, Posti
@sdjohn avatar
'15 GTS300, '86 PX125EFL, '66 VBB, '01 ET4
Joined: UTC
Posts: 8248
Location: San Diego, CA
UTC quote
I'm not totally sure Voodoo, as the scooterhelp wiring diagram doesn't make clear how the switch works on all the connections. I looked at it and noticed it is an identical setup to the one that was in my Serveta and did it the same way as I was taught on that one.
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@sdjohn avatar
UTC

Veni, Vidi, Posti
'15 GTS300, '86 PX125EFL, '66 VBB, '01 ET4
Joined: UTC
Posts: 8248
Location: San Diego, CA
 
Veni, Vidi, Posti
@sdjohn avatar
'15 GTS300, '86 PX125EFL, '66 VBB, '01 ET4
Joined: UTC
Posts: 8248
Location: San Diego, CA
UTC quote
OK, so I went ahead with 6V AC horn, this works fine on 12V AC.

Also, bought some of these:
External inline image provided by member with no explanatory textUntitled by john.headley, on Flickr

My headlight was dimming too much at idle, particularly with the brake light on. Much better now!

Here we are with the running light and headlight:

External inline image provided by member with no explanatory textUntitled by john.headley, on Flickr

And with the brake light on:
External inline image provided by member with no explanatory textUntitled by john.headley, on Flickr

No more headlight dipping! I think they draw like 2W instead of 21W. Nice improvement.
@mjrally avatar
UTC

Veni, Vidi, Posti
73 & 74 Rally, 76 ET3, 80 P200, 06 PX150, 59 Ser 2, 65 Silver Special, 90 V5N 50, 2015 HD Road Glide Special
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Posts: 5078
Location: Oceanside, CA
 
Veni, Vidi, Posti
@mjrally avatar
73 & 74 Rally, 76 ET3, 80 P200, 06 PX150, 59 Ser 2, 65 Silver Special, 90 V5N 50, 2015 HD Road Glide Special
Joined: UTC
Posts: 5078
Location: Oceanside, CA
UTC quote
Good find on the taillight LEDs. Did you find those in a shop or online?
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@sdjohn avatar
UTC

Veni, Vidi, Posti
'15 GTS300, '86 PX125EFL, '66 VBB, '01 ET4
Joined: UTC
Posts: 8248
Location: San Diego, CA
 
Veni, Vidi, Posti
@sdjohn avatar
'15 GTS300, '86 PX125EFL, '66 VBB, '01 ET4
Joined: UTC
Posts: 8248
Location: San Diego, CA
UTC quote
Amazon.
OP
@sdjohn avatar
UTC

Veni, Vidi, Posti
'15 GTS300, '86 PX125EFL, '66 VBB, '01 ET4
Joined: UTC
Posts: 8248
Location: San Diego, CA
 
Veni, Vidi, Posti
@sdjohn avatar
'15 GTS300, '86 PX125EFL, '66 VBB, '01 ET4
Joined: UTC
Posts: 8248
Location: San Diego, CA
UTC quote
Mjrally asked me about red led's and whether they are hard to see during the day. I really didn't know, so here are 3 pics. Brake light off, brake light on with standard bulb, and brake light on with LED bulb.

Brake light off:
External inline image provided by member with no explanatory textbrake light off by john.headley, on Flickr

Brake light on - standard bulb:
External inline image provided by member with no explanatory textUntitled by john.headley, on Flickr

Brake light on - LED:
External inline image provided by member with no explanatory textUntitled by john.headley, on Flickr

Seems pretty good.
⬆️    About 6 years elapsed    ⬇️
UTC

Member
'79 P125X, '78 P200E, '01 ET4, '03 ET2
Joined: UTC
Posts: 11
Location: Denver, CO USA
 
Member
'79 P125X, '78 P200E, '01 ET4, '03 ET2
Joined: UTC
Posts: 11
Location: Denver, CO USA
UTC quote
Recycling an old threat.

Thanks for a great write up on the AC conversion. It is hard to find documentation on this.

I have a, new to me, 1979 P125X (first scooter ever 😃). It is a US spec non-electric start with electronic ignition. The '79 P is a stock 12v system. I have already swapped the tail light, blinkers and flasher relay to LEDs. My head light is the stock AC sealed beam.

I am very annoyed with my battery. It's rather new (1.5-ish years of age) and my battery tender no longer fully charges it. I've tried several different battery tenders and they all have the same result. The bike runs great, however the battery is clearly on its way out. 😡

I'm not super concerned with getting a brighter headlight and my headlamp runs AC off the stator (stock config). My regulator seems to been fine.

I would need an AC horn.

Is my conversion really as simple as removing the battery and junction blocking the proper wires off the stock P regulator?

My regulator has a lot of outputs. Could I run everything off the regulator?

Thanks for any help and insight.
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