Modern Vespa

This whole debacle started with a non-functioning brake light.
I removed the pedal and cleaned the switch, and got that whole thing working, but after that I could not get the cable taught enough to have any rear brakes.
Shoes must be worn out, so I removed the rear drum.
Shoes looked almost brand new, and were not oily or nothing, so I'm kind of at a loss what to do from here.
Just as I'm deliberating how to proceed, I notice an oil drip around the axle seal.

Now, my questions to you; what could cause me to not manage to get any rear brakes, when everything seem to be in good condition, and is the rear seal shot because it's leaking, or does it only seal with the drum in place, and I'm a dummy for not draining the gearbox oil first?

Whats your cable tension set at? You can adjust the cable tensioner and see if that bites better.

Since you mentioned an oil drip, I would thoroughly clean the pads and drum with brake parts cleaner. Then replace the rear seal. I wouldnt worry about the gear oil level.

Could be a dirty drum, could be oily brakes, could be glazed brakes, could be incorrect cable tension? Best to clean them all first, and then follow up with adjusting tension.

Alright, it's always something new just after you've gotten your SIP order in!

I have new brake shoes for it, so I'll replace the seal and the shoes.

I have the adjuster all the way in, but I'd imagine that I'd should be able to at least get them to bite a little bit by just preloading the lever at the back when adjusting the cable? I could literally stomp the pedal to the floor and still waddle around the Vespa in the shop, shoes not even dragging.

Install the new shoes and bring the adjuster all the way back in. Then adjust the cable tension so that you can lock up the rear tire with the pedal pressed all the way down. As the cable stretches and brake pads wear, you can continually fine tune with the 11mm cable adjuster.

You could try loosening up the nut that clamps the cable between the linkage plates. Then push the brake actuating arm forward as hard as you can, pull the cable tight, and finally retighten the nut. This kind of preload is how the clutch cable can be done as well.

Yupp, already tried that, I pushed it forward quite a bit and still no brakes, not even a hint of the shoes dragging. I'm starting to wonder if the actuating cam or the drum is worn down. Does anybody know what the specs on the drum are?

Could be a worn brake cam. I had a worn brake cam on my small frame when I first bought it, before restoring it. It was so worn that it turned completely 45 degrees getting stuck and locked the brakes up. That was fun.

I put in an order for a new cam along with the seal, we'll see if that sorts it out.

The new cam did solve my problem, but I'm not sure it will solve yours. I know this might be a ridiculous question but, do you have the correct brake shoes?

I didn't think about that, the Vespa is new to me and had been sitting for a decade when I bought it, and 4 years ago when I got it running I can't remember if I ever got around checking the brakes. I'll see if the Newfern shoes are the same size as the ones fitted.

I think I found the issue, the rear seal was installed with the lip facing out, and my understanding is that the lip should always face the oil.

Cam looks a wee bit rounded, the shoes seem to be the right size (Piaggio branded, around 60% left of the old ones).

The side with the spring faces in, in every application I've seen.

What does your brake cable look like at the rear wheel? Mine pulls through a pinch bolt, if I had no brakes, I could move the adjuster so it is as loose as possible, loosen up the pinch bolt, pull more cable through and tighten the pinch bolt again.

It's the same on mine, a pinch bolt and the nut adjuster a bit further forward where the cable guide ends. I've tried pushing the brake lever forward while pulling the cable tight, got it around an inch forward, but still no brakes. The adjuster was screwed fully back (towards the rear of the bike).