Rpms required to generate electricity by means of cycling
This got a bit long for a comment:



All motors have a different base speed for the same voltage because of their geometry.  The formal specification for this is Kv, or RPM/volt.

Look for something that has a permanent magnet in it, like Brush[ed/less] DC, and then look for a Kv rating that is roughly close to what you can achieve.  (Note: it may be difficult to find in some cases and must be calculated from other specs)

The permanent magnet ensures the motor does not require external excitation to generate electricity.  Two types of motors that can't do this are Universal and Induction, both of which are very common in AC-powered equipment.  A Universal motor may also appear in DC-powered equipment because it works there too and may have some advantages over a permanent magnet in its intended application.