So, these two articles always merged in my memory, but they were indeed from 2 different issues. Bob Osborn must have dug this family. Sounds like a cool Dad, and he was the Ascot track operator too... so they were in deep.
First from Sept 81... I hope these screen grabs are legible... probably best for a phone where you can enlarge it with your finger tips... anyway, you can find the mag on oldschoolmags of course.
Next... from the April 82 BMXA, the 2 speed mod: