In Indonesia, some youngsters ride old customized Vespa scooters often equipped with makeshift sidecars. Those contraptions are semi-legal but tolerated by authorities. They have no license plates, so they pay no registration fees and have no insurance. Officially, those vehicles don't exist.
The youngsters riding those Vespas seem to be living in fringe of society, like punks or runaways. I don't know how they are called in Indonesian, but since there are a lot of them all over the country, they must have a way to call those guys.