Yes you certainly can. However there are a few things to note.For example, if you buy 6V 30 rpm motor. The lifting mechanisms will go slightly faster, because yours would be 30rpm and I use and test for 20 rpm motors. It would still work without problems, however you will need bigger battery holder for 4x1.5V batteries to reach the rated 6V.Another option is that you check the specifications for your motor and see what Voltage is the minimum. If its 6V, then you need to use 4x1.5V batteries. If however it is 3V minimum, then you can use 2x1.5V batteries and the motor will turn at half the speed, in this case it would go from 30rpm to 15rpm.Also some N20 motors have longer gearboxes. I only use 10mm long ones. Some models however are 12.5mm long. In 95% of the cases these will still work, but things would be slightly missaligned. I wouldn't suggest using more than 50rpm motors. Currently anything past 30rpm was not tested by us..