Modern Vespa

I have a '64 v90 tat had a seriously worn engine and got tired of the impossible to find early engine parts. Found a '74 engine to swap in.

The wiring has me hung up. I only have four wires coming from the stator to the wiring block. Green, black, red, and blue.

My bike has yellow, blue, black, red, and green.

Looking at wiring diagrams I'm not seeing any differences in the wiring year to year. Is there a wire missing from the stator on my "new" engine? Or am I just missing some info?

Your bike:
http://www.scooterhelp.com/electrics/wiring/V9A1.pdf

Possibly the donor bike
http://www.scooterhelp.com/electrics/wiring/VMA2T_USA_wbatt.pdf

If the bike was a 74 USA it would have this diagram, but the colors don't match your description:
http://www.scooterhelp.com/electrics/wiring/VMA2_V9A.wblink.pdf

It's important to have your location in your profile so we can guess the likelihood of you having a USA bike or a rest of world bike. Cheers.

Yeah, I'm in the US. My bike is an American market bike. Don't know about the donor, don't know much about the history of the motor.

Not sure if it will fit, but I think you can put the 64's stator and flywheel on to the 74 motor. I know the taper on the crank is the same.

The '68-'73 looks like what I'm working with.

Did they go DC in '68? I see that there is a regulator/rectifier in that circuit. My bike is AC, non-rgulated. Well, bulb regulated.

The cases and the crank are the same. It will fit.

They're different sizes... The '64 flywheel is much smaller. I'm not sure what the advantage of swapping would be anyway. Makes more sense to me to just sort out the wiring.

'64 case and crank are not the same as the later. Different. Little differences, but different enough that lots of parts do not interchange. Not even the cooling shrouds interchange. I would have rather kept my steel shroud, but it didn't fit over the later jug. I would have rather kept my fan cover as it was painted to match the bike but it didn't fit either. Lots of parts lists show the same bits but that isn't so.

the flywheel and stator are indeed interchangeable.

in fact, before electronic options were widely available the '64 style flywheels were sought out as a lightened flywheel option for a smallframe.

beyond that, the 64 stator will work with the 74 flywheel, if the lighter flywheel worries you.

vespa electrical systems rarely cam be made to work by swapping wires around with incompatible parts; stators, harnesses and switches need to match unless you want to get into some serious butchery,

As it stands I've got 52 year old wiring with a weird rats nest behind my headlamp and odd splices everywhere else.

I kind of figured I'd just buy a harness that matches the stator.

New confusion. Got to looking closer at things.

I don't have a blue wire coming from the stator. When i was looking at my notes must have read brown as blue. Only Red, Green, and Black come from the stator. The Brown wire doubles back to the coil. External coil leads me to believe this is a '74 or so??

I can't find anything online that makes sense. The v50 had an internal coil. Is it a Sprint or something unit? Some of the 12v conversion units are similar?


Such confusion.


Swapping back to my original stator isn't currently an option. I was going to pull the flywheel to investigate what's going on under there but the end of the crank is broken off right at the nut, I wonder if that has anything to do with the interesting grind pattern on the flywheel fins. I don't want to risk pulling anything. I know I'll have to get a new crank eventually but for now it runs and I just want to ride.