What makes an engine a fast revving engine? what are the differences with slow revving engines?

Question

What makes an engine a fast revving engine? what are the differences with slow revving engines?

Answer 1

Mostly the length of the 'stroke'.  Older slow revving engines were almost all relatively long stoke - in other words the connecting shaft (con rod) connecting the piston to the crankshaft was fairly long. Modern engines are short stroke so the piston has a shorter travel.

There are other differences of course relating to ignition timing and fuel delivery but the stroke length is the biggest difference.