Hi.
A random schematic borrowed from the web. Many similar. It uses two capacitors. Called permanent split phase capacitor motor ?
Will increasing the value of a capacitor increase rpm ? I would like that. Or is the capacitor only to start ? Light, please !

 

The capacitor on a split phase motor is selected to match the start/run winding in order for a 90° phase shift to occur, any thing other, will cause inefficiency in the motor, change the value will start to increase heating etc, and result in some loss of RPM.
Max.