Modern Vespa

Hi guys, I'm not an expert, in fact, for the whole thing, I don't know anything about engines etc. I have an Ape Cross 50, I mounted a 102 dr with a 19 carburetor, it started on the first try, the engine sings like a charm, the problem is that as I drove a few km it stopped as if I had run out of gas, I first had the carburetor and the air filter cleaned, but after 6 km the same thing happened, my brother-in-law said that maybe the tank was dirty, I cleaned it, I changed the petrol, used 100% synthetic oil, I walked at night for about 3 hours at low speed, but as soon as the sun came out, it was too hot, it stopped again as if no petrol was passing through, but after 10 minutes it started again, a few metres and it stops again, what could it be?

It's likely vapor lock from the heat. The fuel is boiling in the line, blocking the flow.
Check if the fuel line is too close to the hot engine. Also, your fuel tank cap vent might be clogged.
When it stops, try loosening the gas cap. If it starts, the cap vent is the problem.

I think your sister can do better.

Also, could you look up and to the left please?