Serveta electrical update

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colin
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Serveta electrical update

Postby colin » Tue Aug 14, 2012 2:21 am

So I put in a 12v electronic ignition and a CDI and rectifier (all BGM parts). I have no key for the ignition and MB dev replacement only fits hole in headset, not the smaller Serveta one in the rear, so I'm going keyless until further notice.

With just the CDI hooked up, no issues with that part of the circuit, bike runs just fine (for the whole 0.1 miles I've ridden it so far since it's otherwise bare).

Based on the Stickey's diagrams I've got how to go without hooking through the ignition-key-assembly, but what's not clear is what to do with the DC and AC outputs from the rectifier, since it seems like the loom has those intermixing. I'm looking for a "Existing Serveta battery loom to 12v conversion" diagram, since that isn't in the Stickey's guide or with the BGM products. A quick Google didn't get me any closer.

Figured I'd hit here before I got more detailed and posted on wider boards.
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Zeets
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Re: Serveta electrical update

Postby Zeets » Tue Aug 14, 2012 8:57 am

Can you post a link to the diagram you're using?
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Re: Serveta electrical update

Postby colin » Tue Aug 14, 2012 10:14 am

This shows the wiring loom and what how everything is hooked up to original Motoplat stuff:

http://www.flickr.com/photos/77913212@N ... 574543453/

This came with the new rectifier (BGM) which shows how it would be set up on a S3. As you'll note, there is no junction box on the Serveta. However, the upper right says "Back view of junction box. All connections are bridged for AC power supply. Only green (ignition circuit) and red (DC) stay separate."

http://www.flickr.com/photos/77913212@N ... 574543453/

This doesn't make sense to me, because that would mean everything is wired for AC and the battery is charged but never drawn from? Is that maybe intentional so you'd only use the battery for accessories? (There's other non-battery diagrams in the BGM rectifier booklet that just leave the red DC output disconnected).

If the above is true, and if the 12v horn I bought and all the lights are AC, then I guess that's fine, it's just confusing since the original diagram shows:

12v (presumably AC):
- speedo bulb
- high beam ind
- neutral ind

6v (presumably DC, since it was a 6V battery)
- turn indicators
- headlight
- rear dual-filiment light
- pilot bulb

Yet it all appears to be wired together.
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Re: Serveta electrical update

Postby Zeets » Tue Aug 14, 2012 11:14 am

So, I'll go over the diagrams with better detail later, but with my limited Servetta knowledge and just a glance, you'd be correct. Everything does use AC and the battery would be simply for accessories, similar to my LI. The LI was an older model, but very similar.

The ignition circuit and the charge circuit are separate, and the only function for the battery was for the lights and horn.

Your junction box essentially is your left handlebar switch. The modified diagram you have is for wiring up an older model Servetta, like my LI was you should just ignore the junction box. Its only purpose is to make a couple simple straight through connections where some of the wire colors change (the only electricians worse than the Italians are the British) and add a point of failure. Previously, the left switch didn't exist, it's job was handled by a second junction block (effin Itys) that fit to the back of the headlight, the right switch and the ignition key, which is in the headset. So, basically ignore the junction block. If you sit down with the older Servetta diagram, your servetta diagram and your modified diagram, with a highlighter and trace out all the common wires, you'll quickly see the similarities and will be able to make all the connections.

As far as an ignition switch is concerned, I couldn't find the appropriate switch for my Servetta either and ended up using this. I just wired it up so when the switch was in the 1 position, the battery was connected to the charge circuit and the ignition cutoff was open and in the 0 position the battery was disconnected and ignition cutoff was closed. The switch has 6 poles on the back, the two center poles are the common poles (they're internally separated) and the top and bottom poles are either closed or open depending on the 0 or 1 position on the switch. If you look at your diagram, your ignition switch does the same. You connect your HT coil to ground in the off position and your battery disconnects and in the on position, your battery connects and your HT coil/ground opens.

I learned the stupid way that if the wiring diagram looks overly simplistic to the point of being retarded and possibly originally rendered in a mental institution, it probably is. It took me about two hours of staring at the diagram(s) to realize, "no, I'm not missing something, yes it is this easy and how on the flying spaghetti monster's green earth did I not realize this 1:45 min ago."
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Re: Serveta electrical update

Postby Zeets » Tue Aug 14, 2012 11:38 am

I've stared harder now at the diagram.

Your Jet uses the brown wire, which connects to the battery through the ignition switch and the rectifier from the red wire to power the headlight and all other 6vdc accessories like my LI150 did. The brown wire feeds 6vdc the taillight initially, then the left switch which distributes power to the headlight/pilot/indicators/speedo. The only function of the key switch is to disconnect the battery from rectifier and the 6vdc accessories (except turn signals, which are on a somewhat, but not really separate circuit.)

This is *nearly* identical to the older Servettas, the big difference is that they initially use a junction box, which serves the same purpose as your Jet's: ignition switch, and the four way splice in the brown wire at the stop switch feed/neutral ind feed. What the geniuses at Lambretta did is use 12v 3w bulbs, powered by 6vdc, to essentially create 1.5 watt bulbs for your neutral indicator, high beam indicator, and speedo light. THERE IS NO 12V in the original DC system. You'll need to change all the blubs.

On the plus side, you should feel some level of pride that a company like Lambretta made a difference in some poor mentally challenged, or otherwise deranged, electrical engineer's life by allowing him/her to design circuits for them. Hire the handicapped, you get a tax-break and they're fun to watch.
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Re: Serveta electrical update

Postby colin » Tue Aug 14, 2012 2:03 pm

Yeah, see, I would never guess someone would intentionally use 12v bulbs on a 6v system, but then again, I'm not an electrician :)

So now that I'm all 12v with the conversion, and while I understand everything you said (and yeah, I'd already figured out how the ignition key-switch worked and what it cut on/off), I still don't understand how the battery get's used in this scenario where you said "yeah, it's only for charging the battery" but then also say "then the headlight and such work off the battery". Did you mean the former for the new setup and the latter for the original setup?

Is the original setup actually mixing DC and AC? I didn't think that was possible without things burning out or something...

In the NEW or original diagram, I don't see how the battery CAN do anything for the lights _unless_ the circuit is mixed AC/DC... since in the old the battery feeds to/from the red/brown linked wires (at key-switch/junction box) which feeds everything, which means it has to be mixed OR the whole system is DC. Either I don't know something about mixed systems (likely) or..... ?
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Re: Serveta electrical update

Postby colin » Tue Aug 14, 2012 3:36 pm

I asked a question on the BGM site, the answer linked to what I thought was the same booklet that came with the rectifier, but looks like they updated it to be CORRECT now. If I'm reading it all right, it seems they changed AC/DC layout from the original system. Original system ALL the lights and horn were DC. With the 12v EI stator upgrade and rectifier, they split it so that all the lights and horn are AC _except_ the blinkers, since they're on a separate circuit (grey wire feed). This now makes sense, thanks to the fixed documentation of the product. However, it would help a lot if they just said "With this upgrade, you are moving all the lights to AC by connecting the yellow rectifier output to the brown feed and feeding the blinkers via the red output wire from the stator through the flasher relay which connects to the grey feed." Or something...

http://www.lambrettaspares.com/info/lam ... -+155.html

You'll notice on the original I posted above, the battery bridge in the junction doesn't connect to anything (just rectifier to battery). The updated one linked above shows it connected to the gray and purple (no purple on a Jet200, just the blinkers on the grey feed. So DC feed (red) to battery and grey (really a red to flasher relay which connect to grey which goes to right switch blinker stuff) and AC feed (yellow) to the brown (which feeds all the other lights/etc).

I'll find out if it all lines up proper when I get home...
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Re: Serveta electrical update

Postby Zeets » Tue Aug 14, 2012 3:43 pm

They're essentially using the battery as a capacitor. Since your stock stator probably only created ~90w at ~5000rpm, you'd likely be at a loss most of the time. A stator's output is a curve, and since they have to be optimized to operate with in a normal range, probably 3500-5000rpm on a low revving scooter, it probably only makes 10w or 15w at idle, with about a 35w or 40w demand. Without the battery, everything would go dim. You're only charging at speed. Thus, everything runs off the battery. The other thing to know is that battery technology in 1978 was pretty shitty, so was your charging system. A 5ah battery had to be pretty big, since it was probably rated at 5ah at 75% life. When it was new it was probably closer to 8-10ah. That being said, it probably fell to 40-60% life in the first year or so of operation. Batteries like being charged and discharged in a specific way. Voltages and current that begin to fall outside of their envelope cause rapid damage to the cells. I've spelled it all out here before, but a 12v. system should charge at 14.2-14.4v on a flooded lead acid battery. Charging it at lower voltages, 13.6-14.0v, will cause it to rapidly lose capacity, over charging it will damage it even faster, and I mean 14.5-14.6v over charging. Modern batteries are capable of maintaining themselves much better, but still can go to hell pretty quickly. My Servetta charged at 6.8v @ 4000rpm, which was far to low for a flooded battery. I used a sealed AGM battery, since they're happier at 6.8-7.0v. They have the added benefit of being much smaller too. I've seen guys do niffty things on bikes like the RD and other older battery bikes that don't have starters like using zeener diodes to help control output voltage and use tiny, high-capacity LiPo, Li-ion and NiMh batteries and clean things up. My Servetta had a 6v. security system battery that was close to the same capacity, but about 1/3 the size and mountable in any position.

The original didn't mix, the stator only generates AC power, you use the rectifier to convert it to DC. Since you have a six pole stator, they'll likely use four poles to generate enough AC to rectify into DC for charging and lights, the other two will push out straight AC for the HT coil. It allows the bike run independent of DC power or battery. On simpler systems (RD350 for example) you only have four poles, so you rectify everything and run the ignition off of DC voltage. The problem is, you need the battery to excite the system, and you can't run without it. You'll notice on your original diagram, the HT coil is separated on the stator output. You can convert those bikes to straight AC, I've seen simple kits that use the factory wiring (plus I think you can make it yourself, there are articles on the google) You can rewind the coils, etc. The factory system works ok though, especially since you're converting it to electronic ignition.

The most important thing to know with all of this (and for any electrical system) is that if you have dicey connections and splices, its all for naught. I know you're a pretty fastidious mechanic, but pay close attention to all of your connectors and splices. I've seen too many jobs ruined buy not re-terminating the spade connectors. The original ends have unseen corrosion, multiple broken strands, wire that is broken at stress points inside undamaged insulation, crappy grounds, etc. Take your time, if you haven't already to clean terminations with a tiny bit of emory cloth, if you have goofy Servetta specific plug and socket connectors, solder over where the wire is crimped into the connector (it'll require a lot of flux, and some patience) replace all the original spade connectors. On my Servetta, I went as far as to replace the leads off the rectifier to the battery and the headset with fresh 14ga wire (overkill, 18ga will work). Its essentially a free power upgrade and you don't want to be visited by the prince of darkness in the middle of a 300mi leg of the Corsa.
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Re: Serveta electrical update

Postby Zeets » Tue Aug 14, 2012 3:49 pm

As per the website, that's how I would have guessed they would have done it. It's easier when you see it with out all the damn extra early Servetta stuff mixed in.
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hurleybt
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Re: Serveta electrical update

Postby hurleybt » Wed Aug 15, 2012 9:01 am

On older electronic ignition kits they were all all AC, not DC, even if put on a DC bike. Thought this is probably a totally different (new) beast. I'm talking late 90's.

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colin
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Re: Serveta electrical update

Postby colin » Fri Aug 17, 2012 12:14 pm

Actually it probably follows the same idea, only that old bikes didn't have blinkers, so for the new ones they left everything the same except the rectifier puts out one DC line that goes to the blinkers and the battery. Unfortunately, none of that was obvious to me.

Haven't taken it out for a test run, and don't have any blinkers for the thing right now anyway, and still waiting on a headlight bulb before I can be sure it's all good.

As for all those connections, Adam, I've redone all the ones at the back for all the connections from new stator and from/to the rectifier, but now that you mention it, I'll probably recrimp on new connectors once I get a larger pack of them (only a couple left). Filed off some corrosion from some headset connectors in the meantime and looks like only a couple ground wires in the headset look a little worn...
Last edited by colin on Fri Aug 17, 2012 4:21 pm, edited 1 time in total.
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Re: Serveta electrical update

Postby Zeets » Fri Aug 17, 2012 3:33 pm

The wiring in my Servettas headset was horrendous. I actually found that Berkebile Gum Cutter worked reasonably well to remove corrosion from wiring. A little of that and a fine bristle mini wire brush did wonders. Just be careful of paint. I had the junction block behind the headlight, and all the bullet style connectors that the factory used were half broken off at their crimp. (They were obviously crimped with too much pressure at the factory.) That's when I started stripping everything back a little bit and I soldered and heat shrunk over all the original crimps.
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Re: Serveta electrical update

Postby colin » Mon Aug 20, 2012 12:21 am

Temporarily wired horn through blinker system to test and DC horn and worked great. Problem is, to wire it proper, need to modify the left hand controls since they're all AC now. figured out how I can do it, just need to snip the common supply and solder in a new feed from grey (DC) in headset just for horn (has its own terminal). Hopefully one extra wire in that bunch won't be a problem. Otherwise add another rectifier (bleh) or try to find an AC horn that will likely suck.

Still have to redo an few connections in headset because they're damaged or worn out, but I'm close and at least it all makes sense now.
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Re: Serveta electrical update

Postby tony » Tue Aug 21, 2012 10:19 pm

The moped kids just bunjee a flashlight to the handlebars. Seems like that would be a better approach.
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Re: Serveta electrical update

Postby Zeets » Wed Aug 22, 2012 7:48 am

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