I can see that you're brand new here and it also seems as if this thread is going nowhere. So I'll see if I can't give the info that, I think, you're craving.
These 'russian bike engines' are the closest thing to a 50 cc "Whizzer" that are easily available. Although the russian version isn't available as far as I know. but chinese copies are available and cheap. They are a single cylinder, 48 or 49 cc two stroke. They come with hardware and components to attach to a bicycle. This hardware is not very good and the user usually has to do some of his own engineering. But it's do-able for anyone who has, say, the skill to keep a regular bicycle in good working order. It's not all that hard. But it can be frustrating and aggravating.
They make an amazingly inexpensive and competent little vehicle. The price that must be paid is that you must be willing to tinker and get your hands dirty.
If this subject interests you, then stick around and read these threads. Just click on any headline that looks interesting and read until you're finished or lose interest. Then click on another. You'll learn a lot.