Modern Vespa

ET4 125cc, 1998, 21.500km (about 13.350 miles)

I've been using my father's for two years. Before I started using it, it was parked indoors for about 10 years.

I don't know when he's changed the break pads but lately I've experienced something unusual on both the front and rear breaks:
- The front breaks squeak. Normal, just like a bicycle with worn out pads.
- The rear brakes have twice made me feel like something suddenly got stuck when pressing the break handle specifically while turning. As an unexperienced driver, it was an unpleasant feeling.

A (classic) Vespa mechanic friend of mine took a look and said the front pads look worn out. But from what I understand, the rear ones can't be looked at without taking the wheel and caliper apart.

Now the tricky part: I live in Costa Rica. This model of bike was never brought here by the Piaggio dealer, so their support regarding parts is non-existent. I have to order them through a courier service which makes it pricey.

How can I be sure what the rear break needs before ordering anything and avoid wasting money? What are some possibilities for the rear break situation?

Thank you all!

What you have is commonly referred to as the pre-Leader engine.
I am always surprised at how many parts are still made for it. You can still get new variators, clutches, belts and a bunch of other parts that you can't find easily for most engines that old.
The brake shoes are relatively cheap, and the only way you can check to see if they are any good, as far as I know, is to remove the rear wheel. They tend to last a long time, but your scooter is 25 years old. Rear brake shoes are about $15, front pads are about the same.
If you purchase in the US, just about anything that is exclusive to that scooter will need to be ordered, but the brake pads and shoes are the same ones that are still in use today in some models.
As far as getting parts, Boxcorreos is a service Correos de Costa Rica has set up so you can have them sent to an address in Miami, then they will be sent to the local post office. I'm not sure what arrangements Correos de Costa Rica has in other countries, but this is about the cheapest way to get parts to you.
We ship a lot of parts to dealers in Costa Rica, and if you have any questions, feel free to send me a message, in english o en castellano.

I worked in Correos de Costa Rica for 9 years completely familiar with Box Correos. I'd like to quote the parts with you, sure.