Modern Vespa

Hello everyone. I'm a first-time poster and first-time scooter owner, though I've owned and wrenched on various motorcycles for years (mostly Hondas and Ducatis).

I have a lovely 1980 P200E that runs like a Swiss watch, but I recently noticed that the headlamp has become very weak. It appears to only run off of the magneto, though it does not become noticeably more intense when the motor is revving high.

In addition to the headlight, the green backing light on the speedo has gone out -- this was obviously linked to the problem, as the headlight and speedo "backing light" would flicker on and off in unison.

I've checked the headstock for any obvious shorts and pulled the flywheel/stator to look for any loose connections. Everything looks perfectly fine. Any ideas/advice appreciated!

Do your turn signals work? I'd be guessing your rectifier isn't recharging your battery... or, as much as it used to, anyways.

If you pull out your battery and put it on a charger, then put it back in your scooter, does the problem still exist?

Turn signals do work, as do all of the other electrics. The only things that are not working properly are the headlamp (on full) and the speedo backing light.

There is plainly a loose connection somewhere, as these were flickering before they went out completely, but I cannot find the short for the life of me.

What should the charging voltage be on the battery? Is it like a motorcycle (~13.4 V at 3000 rpm)? I could have a bad rectifier, but that would not account for the (very) isolated electrical fault.

wait a minute. The green backing light on your speedo ( IIRC ) is powered off of the headlight. Like, when the headlight is on, there's a little wire that runs off the back of the headlight and runs over to the speedo to illuminate it. ( at least, that's how all the vintage ones are )

If you've got a ground wire on your headlight that's failing, it might be causing the problem... and it would stay localized to those 2 lights, too.

i think he's talking about the green "neutral" light.

never mind, i didn't read correctly.

try it with the headset cover off, make sure the connections aren't grounding against any of the fork tube or throttle tubes.

Just to avoid any confusion.

-The green neutral light DOES work. It's is the internal illumination of the speedo that does not work.

-The headlight DOES work, but it is very faint.

It has to be some ground/circuit that connects both the internal illumination of the speedo and the headlight. Could this be the rectifier? What is the proper voltage on the battery at ~3K RPM?

Hi mate, At idle it will be "faint" Is it faint through out your rev range?

A good charged 12v battery can run from 12.8 at idle - 13.9 redline (ballsout)

Hope this helps

Cheers

It is evenly faint throughout the rev range -- there is no change in the intensity of the headlamp between idling and cooking down the road at full throttle.

Would a dead rectifier cause this sort of problem? Does that explain the linkage between the headlamp and the speedo backing light?

I'm getting the PX Lighting kit installed for my headlight,
I've blown the sealed P headlight low beam twice in 4 weeks.

Hopefully I'll have halogen by this weekend.

Both the high and low beams WORK, they are just very faint. Rectifier?

Mate, before i say yes it's your Rectifier.

*Have you tried a different bulb, also does your brake light dim too through your rpm range.

*If you have not located a wire grounding under your headset have you checked your switch? Maybe a loose wire there.

I failed to mention in my last post that scooter batteries don't produce the same amp as 12v motorcycle batteries.

*If yes then replace your rectifier

Hope this helps

Cheers

Im having a similar issue on my p125x. The headlight is dim at idle and brightens up when i rev it up? Is this normal? There is no flickering or anything. Thanks.

Strange part for me is that there is no battery. And no stock rectifier. This is an ET3. Just need to look for loose grounds (should not be any, as this is a new harness). Sigh.

normal

Normal as the headlight runs off fluctuating AC off the stator rather than the stable DC from the battery.