Modern Vespa

Is the brake light switch in the front disk brake mechanism adjustable at all? My switch is so fiddly at this point that the brake light is turning on as the brake lever vibrates. The only way to not have the brake light come on is to hold the lever forward with my fingers.

Yes I do have enough brake fluid.

Hal

Probably.

I've never messed with the one on my Sella, but on my Sprint, it screws in and then has a set bolt like a fine-tension cable adjuster, so it's probably similar on the Stella.

So its a pretty stupid simple setup in a few ways. When you pull the lever it opens the switch allowing current to flow through to the light. There is not a lot of adjustment here unless you are not getting enough pull on the lever in which case a washer between the switch and the pump body would allow the switch to open earlier on the lever pull.

That was not my problem however, its that the lever is allowing the switch to open too soon, but there is not a way to change that adjustment. The lever return is driven entirely by the pressure of the brake fluid in the line (and maybe there is a spring inside the pump body).

So maybe what I do need to do is to flush and bleed the brakes with all new fluid. My bike does sit out year round in what is a fairly damp environment so its certainly possible that I need to adjust my expectation of fluid lifespan. A bit of gunk on the piston inside the pump body. I'll try that this weekend and make note if that solves things. If not, I may just buy a new pump and replace the whole shebang.

h

Probably 90% of all moto anything out there uses a basic contact switch in the front brake master cylinder. It's a well proven design. Flushing the old brake fluid with new is always a good thing, but I venture to guess that the brake switch could be the culprit. Try unplugging the two wires going to the switch then unscrew it from the master cylinder. Once the switch is out, try cleaning the inside of it with something (maybe starter fluid?). I'd then test the switch by simply plugging the wires back into it (with it not installed in the MC). See how far the switch needs to be depressed in order for it to activate the brake light. I'd definitely buy a inexpensive brake switch before I spend money on a new MC.

Switch is plastic and its small actuator that touches the lever, wears out. I'd get a new one…

https://www.sip-scootershop.com/en/product/brake-light-switch-piaggio-brake-master-cylinder_58072300

Can this switch be replaced without removing the headset top?

Yes it unscrews out of the backside of the brake lever mount. 30 second job.

Hal

You have to open the top of the headset to get to the connector, though.

I replaced that switch on a Stella about a year ago. The connector on the SIP replacement part wasn't a match with what was in my bike, so I had to fix that, too.

But fundamentally, it's just unscrewing the old switch and screwing in a new one.