Wow! I'm an old guy, so I remember when I was a kid and the "Whizzer" brand bike kits were around.. Surprised such a thing is still available. I had a neighbor that used to put them on bicycles. I know what you mean by the photo..but after looking at the engines I wonder...doesn't an 80cc 2 stroke seem a bit powerful for a bicycle?
https://en.wikipedia.org/wiki/Whizzer_(motorcycles)
BTW: If Skyrider thinks my physical condition requires a mountain bike..well I admit I am 80 years of age, but I am still a working artist/blacksmith. If he has seen the current TV show "Forged in Fire'..he can get an idea of how I amuse myself.