Vespa PX 200 , 2002 voltage from stator

HI there Guys 

Need a little help, just put my engine back in today and now my lights and indicators don`t work nor does my fuel gauge, mmmmmm I think my voltage regulator has gone , but not sure as every thing was fine before I removed the engine, does any one know the voltage amount for the blue wire for the stator to the regulator ? thought id rule that out before I ordered a new one. 


thanks guys  

Hard to say...the unregulated voltage from the blue wire depends on the revs/min of the engine.




You cannot verify the voltage according to the official Piaggio manual without adding a testing installation circuit including 2 switches and an electrical resistor 0f 2.3 Ohm/300W.


It makes no use just measuring the blue wire without the test installation, it could range from 10 to 60 V, I guess.




But please calm down: 


In most of the cases it's only the voltage regulator which failed. 


Otherwise a superficial surveying of the stator plate could tell you if the 4 coils which feed the blue wire are in good order, or if some of the wire insulation failed.


If you want to check this, you have to remove the flywheel and disassemble the stator plate to take a closer look at it.

The coils show several windings of epoxy coated copper wire. In no case there should be damaged segments on the wire (tracks of overheating or mechanical damage. 



Thanks Werner , I have just ordered a new stator and regulator it seemed the simplest option Ill let you know how I get on [:)]

update  - I have bench tested my stator and it reads red/white 112, and white /green 501 mmmm the bike runs fine yet no power to lights and so forth, yet when running I have power to the regulator but when you plug it in the voltage disappears, any ideas guys and girls ? thanks  

Sorry, but you don't have a problem with the stator. I only recommended to do a precautionous visual check of it. Normally it makes no problems but if so, it could be very obvious and visible.


On the other hand a regulator is more prone for ageing related malfunctions (which are not visible, but for sure detectable by a cheap testing installation).


You should be aware that if you buy a cheap south east asian aftermarket stator plate, before you assemble it you have to be 100% sure that it is the identical part.

Also it is necessary that you have to get the ignition timing adjusted (as the new plate is a repro part and the original markings are not trustworthy). I think you know which equipment you need at additional cost?


Sorry...not the easiest way as you thought.


The easiest and most common way would have been that you simply replace the regulator at a cost of roundabout 30-50 EUR and do a precautionous check of the stator plate and maybe a check that the onboard wire harness has no short circuits.

The bench test of your stator is not relevant as you did it, it is not the right method to solve your problem.

Please note that there are 2 separated circuits on the stator plate:

a) The ignition circuit with 1 pickup (red wire) and feeder coil (green wire)

b) The onboard power supply circuit consisting of several coils, connected in series.


So... you only tested the ignition circuit which has no connection to your power supply.
The problem you have refers to a malfunction of the regulator and/or horn rectifier (in case your Vespa is equipped with it)...

As I beforementioned, if the wiring on your stator plate looks ok and there are no VISIBLE damages to the wiring and the power supply coil arrangement (NOT the ignition circuit), you have to replace the regulator and/or the horn rectifier.
This is a known malfunction, there is no secret behind it since the Vespa PX appeared in the 1980s.
My advice was to inspect the stator plate to easily identify visual defects.


Thank you very much for the highly informative information Werner [;)]