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@mjrally avatar
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I just bought and installed this BGM stator as an ET3 replacement.

https://www.scooter-center.com/en/ignition-bgm-pro-stator-hp-v2.5-silicone-vespa-et3-vmb1t-bgm8035

Unfortunately, the brake circuit puts out between 6V and 12V, tail produces 12+ and the headlight 12V+. The real kicker is that when the headlight filament blows, you lose ignition. So you switch from low to high beam or whatever filament you still have in the bulb, and viola you have ignition until that filament blows. (I tried this with all the shitty leftover 1 filament bulbs I had sitting around to test)

So, I've got two voltage regulators installed to make this stator work for the moment. Ive emailed BGM and the stateside supplier who ordered it for me and am awaiting a response. This is clearly a problem. Has anyone ever encountered this?
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Wow that's strange. Prob the stator is wired incorrectly and the ignition is interacting with the lighting. I wonder if the ground on the stator is bad and touching an unnecessary wire or something. Anyway, shouldn't have that problem from a new stator. Since you ordered from a stateside vendor I'm sure you're get it resolved. If you have time, customer service is one of the best reasons to use a vendor stateside when ordering from SIP or ScooterCenter.

BTW, where did you put the 2nd regulator? Did you install behind the voltage coming from the 1st regulator and double regulated the hold bike? Or did you install on the yellow or red wire that powers the headlight?
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I looked and all the wires match EXCEPT, all the grounds go to the same spot. Also, the coils go to ground on the BGM one which Piaggio doesn't do. Normally the ignition ground isn't at the same spot as the black wire (lighting) ground.

Take a look at the BGM image vs the Scooterwest image. Scooterwest matches my original Piaggio ET3 stator.

As far as the regulators, one is on top of the junction box. We substituted a longer screw so that the square regulator could fit on top. Other regulator is in the belly with jumpers leading to the junction box.
Forum member supplied image with no explanatory text
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OEM look a like
Forum member supplied image with no explanatory text
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Little update on things, went for a ride yesterday. Owner stalled the scooter avoiding an oncoming car and it blew the last working headlight filament. (Dozen spares received thanks to Amazon). Not having any spares on us, I connected the brown low beam wire at the headlight housing to ground and had ignition. Obviously no headlight.

So, does that mean it's a grounding wire issue? Where's Rob Hodge when you need him?
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UTC quote
Looks like a grounding problem but where....stator or somewhere on the bike (switch??). Of course trying another good stator would eliminate the stator from the equation or maybe separate the grounds on the stator so the ignition is not sharing the same ground as the lighting. I still can't understand why the ignition system is interacting with the lighting system, even with the same ground but maybe that's the problem?

Sometime Rob pops up on Facebook Scooter Builders Page but not often. He's def a good source of knowledge but Mattgyver is very good and knows all the little details about these electrical system. You can def send him a PM from here and see what he says.

BTW, is this just a replacement or a conversion? Was something going bad for a replacement? You know the bulls*** questions just to get up to speed on what's totally going on.
⚠️ Last edited by rowdyc on UTC; edited 1 time
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rowdyc wrote:
Sometime Rob pops up on Facebook Scooter Builders Page but not often. He's def a good source of knowledge but Mattgyver is very good and knows all the little details about these electrical system. You can def send him a PM from here and see what he says.
I was just thinking the same thing and sent him an IM. Miss his regular input.
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rowdyc wrote:
Looks like a grounding problem but where....stator or somewhere on the bike (switch??). Of course trying another good stator would eliminate the stator from the equation or maybe separate the grounds on the stator so the ignition is not sharing the same ground as the lighting. I still can't understand why the ignition system is interacting with the lighting system, even with the same ground but maybe that's the problem?

Sometime Rob pops up on Facebook Scooter Builders Page but not often. He's def a good source of knowledge but Mattgyver is very good and knows all the little details about these electrical system. You can def send him a PM from here and see what he says.

BTW, is this just a replacement or a conversion? Was something going bad for a replacement? You know the bulls*** questions just to get up to speed on what's totally going on.
Rowdy Rod- I'm leaning with you towards the switch. I'm guessing BGM designed this stator to work with their harness and their DC type handlebar switch. Breaking grounds versus making grounds at the switch (maybe??? Fingers crossed that does it) Luckily, I have one in my stash and will try it out when the owner can bring the scooter back to me.

I didnt mention it in the original post but yes we have tried a different stator. Owners stator #1 was shit. Ordered the BGM one. While we waited for shipping, I loaned him my OEM ET3 stator. All lights and ignition worked. Didnt want to sell my OEM one so I took it back. Installed BGM and now we have what we have.

I'm also going to try disconnecting all the wires for the lighting and see if the ignition runs with just the 3 wires it supposedly needs. If not, then definitely a defect.

My stateside vendor has followed along and is willing to buy me a replacement BGM stator. It's not fair for him to take the financial hit in the ass when his supplier might be sending him crap parts. Were gonna try a few more things before I possibly go that route.
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Alright, i'm here.

so, first things first- the ET3 setup you have is one of the last usages of the goofy VBB2-style no-true-ground unregulated AC system.

it also has the additional wrinkle of having electronic ignition.

in this system, adding voltage regulators is generally not a good idea; because they essentially shunt extra power to ground and there is no true universal ground, in many cases they merely shift the problem somewhere else by dumping stray current into the middle of another circuit. your blowing of bulbs and your interconnection with the headlight may be a result of the regulators. i.e. you are taking the extra power out of the headlight circuit and dumping it into the taillight, pilot or brake light.

also, because of the way this system works, shutting off the headlight at the handlebar switch normally does the exact same thing as you did by shorting the brown to ground, so either it was a coincidence, or your hackery was unnecessary.

there are three grounds to look at here, thet need to be all in common. a bad connection amongst them will cause a system to complete a circuit via some other nebulous manner and can also cause issues like you are seeing. (blowing bulbs, ignition cutting out as a result, etc)

i would look at three points first, to make sure they are all in common.
The black wire, the white wire, and the stator backplate these three are all common ground connections in the systems they are part of. measure resistances between them. you should have no resistance, and a dead short.

Second, i would perform your standard impedance checks, between ground and the red and green ignition wires. you should get ~110 ohms on one of the wires, and ~480- on the other, give or take about 5%. to be thorough, measure from red and green to white, black, and the backplate. if you get unequal results when usign a different ground connection, you have found a bad connection that needs to be fixed.


as a further verification,

measure from yellow to ground. measure from blue to ground. these should measure infinite resistance, no connection.

measure yellow to blue, and you should get some ohms, not dead short or open circuit.

measure from red to ground, and you should get a few ohms. not dead short or open circuit.


the two stators you posted pictures of, while similar, are different. one appears to be an ET3 stator, one appears to be an early battery version of the Ducati setup with a system similar to how a US P or a US 100 sport is set up; most likely it is from an Ape 50 variant.
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Woo. The Hodge is back.
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Rob,

Thanks for coming back. Still working at the shipyard?

A little more backstory, this harness is fairly new. It was purchased from Scooterwest about a month ago and I installed it. It worked fine with my OEM stator and all ground connections are tight and show continuity.

Ok back to the BGM new one...

The voltage regulators came as a result of blowing 6V and then 12V bulbs. I'm burning through them faster than a crackhead with a paycheck on the first of the month.

I've definitely checked the grounds. BGM paints their stator plate a black color but on the back side, the outermost 3/4" edge of it is unpainted. Ive tested it and it does have continuity with the black and white wires and the center part that everything else is riveted to. Also has continuity from the handlebar ground, to the engine case.

Resistance values and continuity in the lighting circuit I'll have to get back to you on. Owner is a few miles away in the next town over.

Included is a better picture of the BGM stator I'm dealing with. Black and white grounds as well as a winding from the Yellow coil (2 o'clock position)

On the other side, the red coils also have their own ground with a few windings going to that. (10:30 position)
Forum member supplied image with no explanatory text
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going to 12v bulbs will cause more problems with blowing bulbs than you had with 6v bulbs.

The impedance of the lighting circuts in this system determines the voltage. if you go to 12v bulbs, the voltage will go up dramatically, far beyond 12v.

if you blow the stock 6v tail, pilot, and brake bulbs, increase the wattage, not the voltage, while keeping roughly the same kind of relationship between the bulbs. (instead of 5w/5w/10w, try 10w/10w/15w, all 6v.)
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UTC quote
rob hodge wrote:
going to 12v bulbs will cause more problems with blowing bulbs than you had with 6v bulbs.

The impedance of the lighting circuts in this system determines the voltage. if you go to 12v bulbs, the voltage will go up dramatically, far beyond 12v.

if you blow the stock 6v tail, pilot, and brake bulbs, increase the wattage, not the voltage, while keeping roughly the same kind of relationship between the bulbs. (instead of 5w/5w/10w, try 10w/10w/15w, all 6v.)
Noted on the bulb choice. I'll try sourcing some spares.

Notice anything unusual with the image I posted? Anything scream thats why things aren't working??
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Rob wrote a really good comment on here a long time ago on load balanced systems. Coming from a DC world, load balanced broke my brain until I read up on it.

Looks like someone fought some similar issues. The pictures might help.
1976 Vespa Primavera 125 ET3 Engine Rebuild Page 3

Does your wiring harness resemble the VMB1 below? If not, what is different?
ScooterHelp VMB1T Wiring Diagram

There are at least 2 switches out there for ET3. The first is what SC is calling an "Italian model" (has 2 horizontal brass strips with on vertical strip intersecting the 2).

The second switch is the BGM switch provided in their conversion harness (just one brass strip going diagonal). They note in the description that a regulator must be used inline for their switch to work properly.

BGM Wiring harness 9077011 PDF Instructions with pictures of wired switch

Hopefully this can help get the issue fixed.
ET3 Italian Model Switch
ET3 Italian Model Switch
ET3 Switch included in BGM wiring kit
ET3 Switch included in BGM wiring kit
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UTC quote
Captcha wrote:
Rob wrote a really good comment on here a long time ago on load balanced systems. Coming from a DC world, load balanced broke my brain until I read up on it.

Looks like someone fought some similar issues. The pictures might help.
1976 Vespa Primavera 125 ET3 Engine Rebuild Page 3

Does your wiring harness resemble the VMB1 below? If not, what is different?
ScooterHelp VMB1T Wiring Diagram

There are at least 2 switches out there for ET3. The first is what SC is calling an "Italian model" (has 2 horizontal brass strips with on vertical strip intersecting the 2).

The second switch is the BGM switch provided in their conversion harness (just one brass strip going diagonal). They note in the description that a regulator must be used inline for their switch to work properly.

BGM Wiring harness 9077011 PDF Instructions with pictures of wired switch

Hopefully this can help get the issue fixed.
Cap,

The harness exactly matches that diagram. Like I mentioned earlier, that harness with a Piaggio ET3 stator works perfectly. I just dont want to give up the only ET3 stator I have.

As far as the switches go, I mentioned something about that at 10 AM. We're currently running the first switch you pictured. Works fine with my ET3 stator.

For some reason I bought the second switch you pictured just for giggles. I just used one successfully to install a SIP Vape kit. Thats what I was thinking of trying next time the owner can bring the scoot over.

Thanks for replying. I'm hoping collectively we can solve this.
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UTC quote
Rob,

You had asked for resistance values. Here you go-
White to red- 96.3 ohms
White to green- 572
White to black- 2.8 ohms
White to the backplate- 2.4 ohms

Black wire to red- 96.3
Black to green- 506.6

Backplate to red- 92.9
Backplate to green- 503.4

Yellow to black 1.3
Yellow to blue .8
Red to blue .8


I disconnected all the lighting wires but left the 3 igntion wires on. No spark.

Ground out the red lighting wire plus the 3 igntion wires and spark.

I tried the BGM switch like Cap mentioned. Horn is always going off. Push the horn button to "connect" the circuit and the motor dies. Disconnect the horn with the same switch and it dies. Horn wire is red, so the horn is grounding, which means its something with the red wire.

Emailing BGM with this info and we'll see what they say.
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UTC quote
I would start looking at that stator. Maybe that one got past quality control and wired up incorrectly. The coil for the red lighting wire would be a good place to start. Some solder maybe touching somewhere and causing problem, wires jacked up, or just a bad day at the questionable labor shop. You may also go far enough and rewire a new stator Crying or Very sad emoticon If you do rewire maybe a good idea to separate the grounds on the stator, too.
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MJRally wrote:
Rob,

You had asked for resistance values. Here you go-
White to red- 96.3 ohms
White to green- 572
White to black- 2.8 ohms
White to the backplate- 2.4 ohms
i think i see your problem. white on this stator is the ground connection for the CDI/ignition setup. it's normally a tad redundant because the CDI has a ground wire that grounds to the case and the coils are grounded to the backplate, but nevertheless these numbers are a bit off.

White and black and the backplate are all grounds. they should essentially be opposite ends of the same wire. the white to black measurement gives me pause. this should be the same as the white to backplate, and it is reasonably the same, however it should be 0 ohms. just shy of 3 is not much, but it isn't nothing, either. combined with the readings on your lighting coils, i think some of the stator components have their grounds tied together, but have a bad connection to the backplate.

measure some things for me, ok?

can you measure the Red lighting wire to the backplate?


these look roughly appropriate.
Quote:
Black wire to red- 96.3
Black to green- 506.6

Backplate to red- 92.9
Backplate to green- 503.4
ok. these are your lighting coils
Quote:
Yellow to black 1.3
Yellow to blue .8
Red to blue .8
something is pretty wrong here. you have some shorts from ground to your taillight/brakelight coil. these readings are probably the soure of your blown bulbs.

i think you are chasing two problems; the blowing bulbs and the ignition. they may not be related. the tail abd brake might not be at least, the hedlight blowign may be as a result of a bad ground connection at the stator, as i also believe the ignition issues are.

i would look at the ground connections on the stator, possibly resoldering them. if you want to get swap-happy, you could try using the black wire in place of the white wire on the CDI, and then do the same while grounding the white wire. see if that fixes it. you could also try connecting the white wire from the stator both to the case and the white terminal on the CDI.
in effect, i suspect the connection to ground between the components and the case is high enough resistance to cause issues, and the system is finding a less resistave path that still is far from ideal thru the headlight coil, as it should be the only lighting component with a path to ground on the stator.

additionally, i think you have a bad tail/brakelight circut that has a short to ground.
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