MGBR36 is a minimotor right?
They on a 26 inch wheel at 48v have had its fair share of threads all over with people with burnt motors, Id say no. Don’t do it.
Even on a 20" I believe there may not be enough resistance in your motor coils to take this kind of voltage at full throttle, you will have to change the PWM.
You can do it but you need to limit the throttle. The motor will still get 48v but not as wide pulses, so the bike should go as normal speed on hills but on flats sling shot ahead with the higher volts. You would need to balance power and speed perfectly.
To give you an example I have a 24v brushed motor. It will run fine at 24v and 35v on a 20" wheel It burns out at 36v on a 26" wheel and it will burn out at 48v on a 20" wheel.
And then you need to consider the gears in the motor may not be designed to go at such high RPM at 48v and on a 20" wheel. The 20" experiences less resistance on the motor so wheel is allowed to make good torque from the RPM. This will put less KG on your gears but the RPM may be over what the materials are designed for. RPM can make heat on your nylon gears and excessive wear as well.
I think you should keep the mini motor at 36v and purchase a larger motor like the HBS or the
MO MP then you can go all a lot further with the volts.
