1900-1920 motorcycle??

[Archaic]

What kind of motorcycle is this??

[L.A.B.]

Not really a motorcycle at all, but a "motorized bicycle" and nowhere near as early as 1900-1920.

The "Jet" engine kit can still be bought new.

http://www.kingsmotorbikes.com/Jet-48cc-Black-Finish.html

https://www.google.co.uk/search?q=jet+80cc+bicycle+motor&client=firefox-a&rls=org.mozilla:en-GB:official&channel=sb&source=lnms&tbm=isch&sa=X&ei=BzkSU9iLKvLB7AapvoGYAw&ved=0CAkQ_AUoAw&biw=1336&bih=707

The bicycle appears to be a "Greenline Beach Cruiser"
http://www.copacabanabikes.com/greenline-beach-cruisers-m-5.html?sort=4a&page=1