Modern Vespa

I've gotten rid of most of the bugs in my P 200 E at this point, and it seems to work fine doing errands. But it works better than I do because at this point it's getting pretty damn cold around here. I have a Kanetsu electric vest that draws 3.3 amps. How much juice does the P Series electrical system put out, and could it spare that much?

Mike Taglieri

Headlight 35 watts
Tail light 10 watts
Stop light 10 watts
Indicators 21 watts (plus whatever the flasher unit draws)
Speedo 3 watts
(The figures are guesstimates but close enough.)

So about 79.

Plus vest @ 3.3 amps x 12 = 39.6 watts.

118 watts all up. Standard stator is something like 80-90 watts when running at (not sure) revs... certainly not at idle.

You can get a 120 watt stator but you probably have one of the 7 wire types which makes it not exactly plug and play.

http://www.sip-scootershop.com/en/products/stator+plate+piaggio+for+vespa+_23387100

Better idea - depending on how long you need it for - is to buy a smallish deep cycle battery, put it in the glove box and run it directly from that, and recharge every time you use it.

if it's an early US style P, you have less to deal with than you think.

those run a separate circuit for the headlight and the battery circuts.

those have about 40w for the charging circuit.

get an LED tail/brake light bulb. this will cut the consumption of the system to under 1 amp.

this will give you between two and two and a half amps of extra power on the charging circut.

i'd upgrade to the battery for the electric start model, especially would recommend the new SIP sealed ones.

this will up your battery from 5.5AH to 9 AH.

unless you are doing several hour long rides, this should work. expect the battery to last a season, maybe two. they don't like to be deep cycled.

invest in a trickle charger, and keep the bike on the charge when you park it.

Does the jacket draw continuously? Since it might warm up and come on and off to regulate the temp?

Just run it and monitor the battery voltage with a cheap display. LEDs would help.

Thanks for the ideas. It's actually not as bad as it sounds during normal running, because the indicators are very seldom on (and not at all on this bike. They were working OK when I got it but not now, so I give hand signals).

Also, on this bike the stop light is only on when the rear brake is on. If it's supposed to work with the front brake too, that broke and I prefer it that way. Years ago I modified my Norton Commando so the brake light only works when the rear brake is on. That lets me sit at traffic lights holding the bike with the front brake without using any juice. (Old British bikes are just as alternator-challenged as old Vespas).

So, using Rob's numbers, the total drain during normal riding should be just the headlight, tail light and speedo, for 48 watts (51 at stop lights, because the neutral indicator light is on and it's probably the same as the speedo).

This whole system seems rather strange. In every other bike I've ever worked on, the system turns the whole output of the alternator into DC and uses it to run everything. If I understand it right, this system leaves the output to the spark plug as AC and only rectifies the output that powers the lights. Unless I'm missing something this seems more complicated than necessary. Do later Vespas do it the same way?

I've also discovered that I can't start the bike with a dead battery, but since many Vespas don't even HAVE a battery, I don't understand why that should be so.

Mike Taglieri

you've misinterpreted what i said.

US market P's run three separate electrical systems. the AC system for the headilght, the ignition, and the DC system for everything else are totally separate, and run off different coils.

there are a number of different systems used on Vespas, for instance, early 60's bikes run two or three separate AC systems in addition to the ignition, to get away wth not using a regulator. Later P systems run a system that takes al lthe AC from the Stator and runs the headlight with it, with any extra going into the battery. Some really late systems go even wierder, runnign the headlight off AC, and the Turn signals off DC, but the brake, tail pilot, and speedo run off DC when the engine is off, and AC when it is on.

but back to yours. the brake, tail, signal, and speedo light run off DC. this DC system a pair of two coils that charge it, and those are around 30-40w output.

my normal qualifier here is i that have simplified and generalized a few points in this explanation.

There are effectively 2 coils delivering AC (in the US case going straight to the headlight), and 2 DC (for everything else) via the battery. The spark is fed by the yellow-coated coil, and sparks timed with the (hall effect) pickup.

Would it be possible to beef up the coils' output by rewiring them/adding more wire? Or, for lack of a better alternative, given that a typical headlight bulb is around 30/35W, just rewire the stator to dedicate just 1 coil to AC, and 3 to DC? Not sure if the Cosa stators were made to deliver 120W by simply wrapping the coils with longer/thicker wires, and if that's the case, why stop at 120W's worth? There are probably some basic electrics rules I'm overlooking here, but it would be nice to know if there's an easy method to garner more electricity based on the current setup...

The way Vespa constantly changed the way the alternator system worked makes me finally understand why the manuals I seen online have so many different wiring diagrams in them. But none of them seem to be right for my bike.

The clearest ones, because the wires are colored, are the P200E "before 1979" and "after 1979" diagrams at Scooterhelp.com (http://www.scooterhelp.com/electrics/pages/VSX1T.p200.html#euro_after)

But my bike IS a 1979. Does that mean it's different from both the ones before and the ones after, or is this just a mistake in the title? Also, my ignition switch has 4 terminals and all of the diagrams here show switches with more (with one exception. The diagram for the P200E with key and battery before 1979 shows a switch with 4 terminals, but the close-up in the lower left of "Ignition Switch Connections" shows more).

Can anyone point me to a wiring diagram for the '79 P200E with turn signals that's actually completely right? If I had that I would probably still be confused, but I'd be confused on a higher level.

Mike Taglieri

Mike, I'm not sure I get the question. Among the wiring diagrams there are 2 specific to US models (with neutral indicator, and different color wiring); the 2 first ones. The others are Euro models, and are likely to be different from yours.

Is your P2 not reflected in this diagram?
http://www.scooterhelp.com/electrics/wiring/VSX1T.USA.after.pdf

Scooterhelp's wiring diagrams, in any case, aren't gospel: this one ( http://www.scooterhelp.com/electrics/wiring/VSX1T.px200e.batt.pdf ) has the turn signal light in the speedo miswired (the wire common to the turn signal and reserve lights is the gray wire, not the red), and there's a diagram for 6V points ignition for the P200E ( http://www.scooterhelp.com/electrics/wiring/VSX1T_Euro_6V_Points.pdf ), which AFAIK never existed. The early P125Xs were poiints, whereas the P200Es were 12V electronic from the start (unlike the 125 blocks, there were no points models to carry over from previous models: the Rally 200 was already electronic).

The problem with that diagram is that it shows an ignition switch with six terminals (though numbered up to eight). Mine has four terminals, so it looks more like this http://www.scooterhelp.com/electrics/wiring/VSX1T.USA.before.pdf and this http://www.scooterhelp.com/electrics/wiring/VSX1T_Euro_before.pdf

But I'm not sure even these are right. I replaced the ignition switch on my bike a few weeks ago (there was nothing wrong with it -- the keys are just so hard to find that it was easier and cheaper to replace the thing than find a key blank). If I remember right, my switch had only one terminal with two wires coming off it, and they were both black. Both of these diagrams have multiple green wires coming off a terminal. Also, my switch does not have a Park position -- just on and off.

It would be nice to know my actual wiring diagram, but I can live without it for the time being. For the electric vest situation, I think I'll install an LED tail light and a small digital voltmeter in the headset, connected either to the red wire or to a wire that's hot when the key is on.

from your description, you have an early US P.

changes on these scooters are not formally delineated by model year; Vespa did not even assign model years until the mid 80's, only recoding the date of manufacture. Changes are specified by happening at a specific VIN; for example before Vin 50032, the US p200 had a 24mm carb. after, it had a 20. the wiring system changed at vin 34627. this happens to fall in the range of bikes produced in 1979.

take the wiring diagrams from Scooterhelp with a grain of salt; these were re-drawn by Dano in the early 2000's and are not from, or endorsed by piaggio in any way. some of them have minor errors. like forgetting to take off the diagram for the 8-pole switch on his version for the early US P.

Even at that, with the correct diagram these systems are not the easiest to understand. there are some interesting design features and choices, some that make little sense today but were perfectly valid with the technology available at the time.

like the split system; on an early P like yours the headlight has no regulation in the circuit. it balances the coils against the headlight bulb. noone would do this today, but at the time solid state AC voltage regulators were fairly new technology. hence, the system was designed to function without one. it's more finicky than a regulated setup, but at the time was more tested and was cheaper to produce. in addition, the reason they run two systems, (an AC and a DC) is that the AC system is inherently more reliable; if your battery system fails you still can drive home with a working headlight.

On the other hand, if your engine fails on a DC system at night, trucks coming up behind you can (if lucky) still see you, while you walk your scooter across the fwy from the fast lane to the other side (tested this myself )

mike:



Is it wired something like this? This is the simplest set-up, where the circuit is closed by default including the engine kill, and turning the key to ON just breaks the contact for the kill (un-grounds the ignition). This works on an AC, battery-less system. If yours retains its DC, battery-powered electrics, it needs to connect the battery to the electrics when the key is turned to ON. The park function usually connects the lights switch to the battery, while keeping the engine grounded.