These are very scary MOTOR cycles and not just for the rider!

[Ishrub]

Suppose you've got up some momentum on such a steed, the fan is pushing hard and you come hurtling around a corner to be confronted by Farmer Brown's cows. These days, you'd shut the throttle and get on the brakes. This bike doesn't have any brakes, and adjusting the throttle speed (i.e 50 mph self-contained gale) requires tinkering with the fuel-air-mix at the motor, which is two feet behind you. Hence, there's no immediately available throttle adjustment and no kill switch either, so you're taking your own meat grinder to the picnic.

The Aerothrust propulsion system: An insanely great idea

It might look dumb, but this little engine catalyzed the American Air Boat industry, and its legacy might yet have several more significant chapters in general transportation. Pusher engine technology can create very efficient vehicles, capable of doing things better ... maybe even for personal…

newatlas.com

Another
This is a 1914 Excelsior 28” bicycle fitted with the twin-cylinder Aerothrust engine driving a 40-inch propeller

 

[Sparky59]

All of those bicycles had coaster brakes....I built a motor bicycle when i was 14, Had a 5hp Brigs w/belt clutch down to pedal hanger shaft w/sprocket and chain drive back to a archer 3-speed rear hub.....20" stingray bicycle....w/english racer scrub brakes...( meaning NONE at all)
She would certainly GO but the best 'Ya could do was hope for a hill to slow down.....