I have some problem upload pic it said "There was a problem during the uploading of d2.jpg." I will try later again.
About it.
Robin2:
You have not said what you are powering the motor with - volts and amps available?My guess is that you need a driver that can handle a lot more current than an L988 can. I think I had a motor like that years ago that could take 9 amps for a short period. And for that I would use a driver that could handle about 15 amps.
Maybe an Electronic Speed Control (ESC) would be an economical option. They are controlled like a servo.
...R
Yes, it looks like this because when motor works the driver became very hot. I thought about ESC but I don't quite understand how to connect it to motor because motor has only two wire but ESC need 3?