Steel Riders (1987)

An eight part children's thriller involving stolen jewels and BMX bike riders. A new life begins in the big city for the Mitchell family until what a horribly wrong happen and Sandra, Mike and their father Brian become embroiled in the theft of diamonds and emeralds. Jailed their father, bot children must be survive by themselves for to find the truth and to save their father, but a mysterious biker dressed in black will try to stop them anyway.