Modern Vespa

I've finally had it with the femsatronic and ordered the vespatronic. I really really wanted to keep the stock flywheel but also want to ride the bike. so it goes.

In preparation I've gathered diagrams from:
'74 US Rally coversion to AC only
1974 Rally 200 - Batteryless but still 6V?

For more than 30 years I have lived in fear of 1974 US market Vespa wiring, but it's not actually that bad and I don't see the conversion being that hard at all. The most confusing part is that there are 3 different wires that head out from the battery/rectifier. One powers the headlight, taillight, and speedo bulb, the second powers the turn signals, and the third powers the horn and brakelight. But even though they come from different positions they are all powered from the battery.

OK, next figure out the Vespatronic.

Last edited by oopsclunkthud on Sun, 10 Jul 2022 14:37:26 +0000; edited 1 time

Hey Patrick, it is as easy as can be, you already have it sorted out. It is also really easy to run a modern cdi on the Femsa pick up and flywheel if you want to go that way. Can even run 12v lighting on the old Femsa with some simple mods...

All you need is to change all bulbs to 12v...if your horn is dc, run it off of the dc side of the regulator. Everything else can go off of either ac or dc, your choice...

I prefer to build a new harness but you can use the existing. At a minimum it is good to pull a 16g pair of wires to the headlight so you can take advantage of the power the kit puts out and run a bright headlight.

Do you already have the kit in front of you? Does the 4 colors off the stator match the ones in the diagram?

I take it you've already seen this?

http://vespa-klub.dk/Rally_CDI.HTM

Should be delivered tomorrow.

From the diagram for the Vespatronic it looks like Yellow-White is used unregulated for AC, and the White-Red is rectified for DC. If you don't use one or the other do you leave it disconnected?

In other cases my instinct would be to make a new harness but I'm reluctant on this bike and it looks like it's not needed anyhow.

If you don't use the unregulated AC I'd just let it float at the junction box where there's plenty of room and a secure terminal holder.

You shouldn't have to make a sub harness just to get that to work. You could use one of the yellow wires from the junction box to regulator (I'm assuming you have a double yellow Rally stator?) And then from there make a pigtail to combine the green, green/white, red and maybe brown?? (My memories foggy on the colors of the turn signal relay) and that's it. The supplied regulator can get tucked somewhere by the battery box.

I'm too cheap to buy the Vespatronic so let me know how it works out!

I'll probably use the second yellow to run the AC over to the battery side. May run the headlight off it.

Are the two really completely independent? Seems a waste.

Stator seems to be sitting too tall, keeping the flywheel from seating.

it's not the flywheel itself (lapped to the crank) or the key (lapped to fit) or the backing plate, everything clears there.

The plastic around the LT ignition coil is the first thing that contacts but not sure yet by how much. More measurements to come.

Curious to see what you find, have never had a clearance or fitment issue with Vespatronic...

Put the flywheel on and measured the gap between it and the case where the stator seats, 10mm.

Put the stator and flywheel on the surface plate with the flywheel touching the plastic coil guides and there is 12mm from the face of the stator to the flywheel.

So the stator needs to sit at least 2mm lower, 3mm for a bit of clearance. Resolved in a lathe this afternoon.

and since one modification triggers more, had to take .5mm off the other leg of the stator and put a cutout for the solder blob.


plastic bit needs .5mm more clearance, solder blob needs a bit too

that came out better than I expected my mill to do

all better

Nice work, so much cleaner than rotary tool/file adjustments!

Still surprised it did not fit out of the box!

I'd expected it to just fit as well, but then no other scooter parts seem to just fit so not sure why I'd expect that.

Need to make a mounting bracket for the coil. going to place it in the standard rally position. Given it's a lot lighter I'll make the bracket from aluminum.

I really need a small press brake. The bracket came out ok, not great, but it will work for now.

Bracket looks like it came out perfect! Nice job.

thanks, but I picked an angle where it looked the best and didn't show my hammer marks, scratches, uneven legs, and the washers hide the mess I made of the holes.

Then I went and searched for vise brakes, then decided a small arbor press would be better, then found and bought a really cool arbor press that will be too small for this, but couldn't pass up.

So, in the end I got a working bracket and more tools on the way.


the cool press I picked up

Flywheel is fitted and roughly timed to ~25° BTDC at idle. Was having some float issues and dumping fuel, new float fixed it. Junction box at engine all wired and starting in on the battery side.

As I want this to be reversible and this bike has not been mucked with too much, I'm mapping out the stock wiring first.


stock regulator wiring
1974 Rally 200, US market

Stator is wired to allow for AC or DC setup.


Stator supports AC or DC

DC regulator wiring

AC regulator wiring

Made a small cover to tidy up the patch wires and the leads that will not be needed. Needs a bit more work but needed to see how it would all fit together.

Sweet! Now replace that rusty bolt.

Got the patch wires done and in place, and rev 3 of the cover to tidy things up.

why can't scooter parts ever be documented in a way that actually gives some useful information?

Since my initial interoperation was clearly wrong this is how I think it is intended to work.

In the image below terminal 3 (lamp) is an AC shunt and has zero to do with the battery. Any DC load must be run off the +B Battery side of things (normal but not documented that way).

Not only that but the wiring diagrams utilize different methods of wiring which makes it extra frustrating. I think you have it right:
Lamp is regulated AC
B+ is regulated DC

Here's my updated DC diagram:


but with a 12V battery.


Last edited by oopsclunkthud on Fri, 21 Apr 2017 14:44:48 +0000; edited 1 time

I'm still wondering what the white wire does

The white from the stator is the full wave 6V leg from each of the coils that are the yellows IIRC, it has been a while since I looked at a 74 setup. Since it is common to both coils, there are some options :

Ground one yellow, do not connect white to anything, the other yellow gives 12V AC
Ground the white, both yellows give 6V AC (although half wave)
Connect like the factory with both yellows and the white going into a pair of full wave rectifiers (in one box) and get a nice full wave 6V converted to DC

Nice answer.

I'm struck by the thought that if oops ever sells one of his bikes that I probably want to buy it . Thorough, thoughtful work going on with awesome attention to detail.

Just tested, correct! The white is a center tap between the two yellows. The odd thing is that when the key is on the white is connected to +6V, not ground as it normally is in a full wave DC setup

Indeed.

The white going positive when the key is on is just the back feed of the battery...

got it, I think.

in the prior diagram I posted the diodes were set so that the center tap of the coil was the low side or ground. In the Rally I think the diodes are flipped so the white get's pegged to the +6.

That would imply the inside of the rectifier/regulator works as follows. The white gives the positive current out and is connected to a red wire that joins the brown at the fuse block. the white/red/brown is all regulated by the brown connector on the regulator with most likely a zener, resistor, and capacitor but however it's done that is where it's done.

So the Yellows plays the rectification game with ground, letting the white be the DC out. Then the brown regulates the whole thing.

Got things rewired per the updated vespatronic DC diagram and all is well so far. Did some clean up of the headlight wires, found the bulb holder was upside down, all is well now.

here's the file for the regulator cover, in case anyone needs it. The hole spacing should work for any of the larger rectifiers from '74 on.

RallyCover4.stl.zip
Description:		Download
Filename:	RallyCover4.stl.zip
Filesize:	278.82 KB

Took the bike for a short trip to fill the tank (forgot how much I love oil injection). Was slow to warm up but then was fine. The flywheel is a bit too light for taste but have the aluminum fan on order so that should take care of that. The timing may need a bit more advance in the stock form but plan to do some work on the head, so I'll live with it for now.

Anyhow, all set for Classico Moto Italia Venti (VCLG - San Jose CA)

Was going to start a new thread, but want to keep all my Rally changes in one spot, so here we go.

At this point I've taken the Rally on the Moto Melee 3 times and countless other long rides with the engine dead stock (other than the vespatronic). No drilled air filter, still running the pilot jet that does not have the air hole in it...

It's the only bike I have that does not have EGT/CHT gauges and there was a freedom in not knowing, just keep it all original and ride it. And that has worked until the stock exhaust packed it in.

So before changing anything I wanted to get a baseline EGT/CHT. Patched the exhaust up, fitted the gauges, and went for a 50 mile ride, mix of city, freeway, twisties, steep grades.
Under load both the EGT (650°C) and CHT (200°C) were right in the middle of the safe/happy zone. WOT pulling a hill the CHT would climb to the limit but not go over, and the on the down hill maxing out the speed the EGT would climb to the limit but not go over. So it would seem Piaggio set the bike up correctly from the factory 48 years ago. No wonder it's been so reliable.

Installed an SIP Road 2 and while it does have a noticeable increase in power, at partial throttle and at lower rpm it's got a lot of flat spots. It's also as loud as it was when the stock pipe had a big hole ripped in the top of it. People like these things?

Went from a 118 main to a 122 to get the temp stable at top freeway speeds. I'll find out this weekend what impact that has on the fuel economy.

Mr. Owens, I know that we briefly texted about this earlier.

but maybe an experiment with a drilled filter, and bumped idle (or even a bell) might clear up that midrange stumble? the 120's MJ kinda tracks.

I'd be interested to see what the result would be with a T5 set up 24G & AF or a 26

as long as that pipe isn't as loud as a blowed out simonini, call it a win!

I'll experiment more after the ~600 mile weekend, for now the stable high speed temp is enough. I'll have all my jets with me but really only expect to have to lean out the main a bit for Crater Lake.

color me jealous. I expect a full report and experimental phase after the fact.

Yeah, that's the sound!

And don't be fooled, guys, by others who say the Polini box is quieter. It sounds less like you describe (the bright pop), but louder in the lower tones:

https://www.youtube.com/shorts/nROgiPZi5vM