Exterminators of the Year 3000 (1983) on Netflix

The year 3000, after a nuclear war turned the earth into a desert. A group of survivors in a cave runs out of water and desperately needs new supply. The last guy they sent out didn't return. His 10 years old son Timmy wants to join the next team. They know where they'll find a well, but the problem it the way there, which is controlled by a savage gang of motorcyclists under the bloodthirsty Crazy Bull. A lonesome stranger who Timmy meets on the way may help.