Modern Vespa

I have vespa ET4, 2001, approximate 35,000 miles (odometer cable broke about 5 years ago).

The symptoms.
1) battery is 1 year old.

2) It is currently Nov.

3) battery was trickle charged over night. Reads 12.6 volt

4) scooter starts very strong. Ride to work (4 miles, 30 minutes, city mile).

5) almost at the end of the ride, head light gets dim and horn doesn't work (sign of weak battery).

5) with engine on, use spare key to open the seat cover, check voltage. With voltmeter, it reads only 10 volts with engine on.

6) if scooter engine stays on for another 15 minutes, voltage drops to 9 volt and i have difficulty keeping engine going.

7) replaced voltage regulator with spare on. Battery trickled charged over night. Symptoms (1-6) are repeated, so it is not the voltage regulator.



8 ) With battery fully charged over night, voltage regulator removed, engine ON, checked voltage of one of the three yellow wires connecting to voltage regulator. According to vespa manual, 3 yellow wires are for 3 coils from stator (alternator). I get zero voltage between yellow and ground (for each of the three yellow wires.

Repeat, to read the voltage, with engine ON, voltage regulator was disconnected. For ground, I used metal part of the scooter, so no need to question whether ground wire is faulty.


Does this mean my stator is dead?

I regret, I didn't get to check the Ohm as specified in the manual

If stator died, why would all 3 coils die together?

According to ScooterWest, Stator plate for Et4 is $60. With Flywheel and magneto, it is $153. Any advise, any experience?

https://www.scooterwest.com/catalogsearch/result/?q=et4+stator

I want to add one more symptom. With battery fully trickle charged over night, engine ON, if I remove the battery by disconnection ground wire returning tot the battery, the engine dies. In the past, I noted that for my scooter, after engine started, I can disconnect my battery and the engine will not die.

It does sound like the stator. The flywheels in the ET4 were also notorious for coming apart.

We have the stator for about $50 and the Stator and Flywheel for less than $100, both OEM parts and both in stock.

You will also need a flywheel puller.

you solve it? I'm seeing the same item it looks like. my battery charged works, i think it is a stator issue. bike died but it cranks and has no spark from sparkplug. i don't know if that would be issue if spark plug cranks.

~2018, at the time of my original note, it turned out to be stator (magnet in the stator was cracked and crumbled).

Then around 2 years ago, I got similar symptoms again. This time, it turned out wires coming out of the stator was rubbing against part of the engine, and one wire was cut (years of vibration and rubbing). I then fix that wire. Now, no problem with stator, charging, starting, etc.