Modern Vespa

2003 Stella with stock headlight set up. No problems since new but now I keep having the bulb blow every 10-30 miles. The low beam will blow, so I will start running with the high beam until that blows too - usually a day or two later.

I found a loose wire at the switch and took care of that. Found some bare wire and took care of that. And I'm still blowing the headlight bulb.

No other electrical or light issues - just the headlight bulb.

Any ideas?

I had exactly this issue with my PX; headlight and dipped beam blowing after a few miles of riding (brake and tail, similarly), but no such issues with indicator bulbs.

Remedied by replacing the reg/rec unit with a Ducati item.

There are two different ways in which a bulb can fail. Either the filament breaks mechanically through vibration or it burns up through getting too hot. If you look carefully at the remaining filament and envelope do you see signs of burning such as black or white ash? If the filament has just disappeared do you see the broken bits rattling around? If the filament appears to be intact flick the bulb with a finger nail and you will probably see a break where one side vibrates and the other does not. If there are signs of burning the bulb has probably suffered with too high a voltage and this can be checked with a volt meter as you rev the engine, or you can even just observe the brightness of the light as you increase rpm to see if it gets brighter to the point of failure.

I should have said that there is a third cause of failure where air leaks in to the envelope but this is extremely rare on modern bulbs.

If the voltage regulator is faulty, you tend to get voltage spikes which will blow the bulb. Your indicator and tail light globes will also go. Change the regulator and also fit a halogen main globe, they can handle voltage spikes.

Thanks for the replies.

I replaced the regulator and now everything is back to normal.

I ordered a "Ducati" brand from Scooterwest and received an "RMS" brand made in China! No time to send it back - I need to get back on the road....

This was fairly easy to do after reading the instructions.

Her's some pics:

(Actual Item May Vary from Image)

That can be interpreted in at least two ways.

So it works and you are happy now.

I doubt Ducati ever made their own although they did start as an electrical component manufacturer.
Would have been Magneti Marelli or .....

fishFingers: RMS is meh. I hope your regulator lasts but from experience that wasn't the case when a customer wanted something cheap (they go for 25EUR here). Ducati ones go for 55EUR... Ducati Energia is a subsidiary of the Ducati Group. They also have their own huge, "Ducati Energia Group". They build their stuff inhouse. Piaggio has stopped buying many of their regulators (especially for the P/PX series) and they have turned to the shitty Chinese (Kokusan) & Indian (Swiss) manufacturers.

https://www.ducatienergia.com/index.php?lang=en

My "supplier guy" buys directly from Ducati so we are still lucky to have quality electronic spares...

This regulator will go on my blue P so I can install a battery and turn the system to AC/DC...

Honda ones are cheap here in Asia ($15) but Honda do not have a good rep. for regulators. Yamaha better. Also plugs probably not compatible.
On my NSR 250 I use one from a CBR150.

Not only did they send you a cheaper version of a reg/rec, I believe they've sent you the wrong type. Have you checked your battery charging with it fitted?

You know, this was also bugging me. Usually the regulators with the A-A terminals are for "floating" type of stators. The OP though is in the US so maybe their electrical circuit is also different...

That's correct it works with isolated charging coils.
However, the description of wiring it, to the Stella on the scooterwest site, suggests that they don't know how this reg/rec works

Well it seems to be working very well so far. No more blown bulbs.

The regulator came with instructions - see attached photo. Scooterwest intended it to be used on a 2t/4t Stella.

Yeah, read that, but as I said it doesn't make sense.
It was the AC side of the unit that failed on your original, only the headlight and a few instrument lights run off this. All the rest is DC including the tail light.

Put a voltmeter across your battery and see what the voltage does when the engine is revved. If you're not seeing between 13-14v your battery isn't going to charge. My guess is, with that rec fitted the voltage isn't going to change.
If that's the case and send it back and get the correct Ducati type that you've paid for.