The FS1E was a 4 speed, not 5 speed as stated in the text. It had a real world top speed about 45mph with a skinny youth on it. There was a yawning chasm between 3rd and 4th gears. On the plus side, it was stylish and invited the rider to it, and the engine was nearly indestructible provided there was a reasonable premix in the tank.
The bike to have, a genuine 50mph plus, 5 speed gearbox, was the Suzuki AP50.
Kawasaki did not enter the moped market in Britain until the 30mph law was introduced. Honda's SS50 had a 4 speed box and a small carb and had poor sales.
Racing, the Fizz was always struggling due to the gap in the ratios and restricted availability of metal to allow bigger transfers. 60mph tops on race gearing, with an A100 clutch shoehorned in to stand the slipping needed between the top two.
The AP was always much better and eventually Team Ape managed to make theirs competitive with Kawasaki's later AR50 on performance, but aged metal and back of the sofa change for a budget meant they also developed 2 part pistons or crankshafts.
The Ape bike