Yes! Of course you can. Most outrunner motors used for e-skating have a minimum of 4 screw holes to attach the motor to the motor mount. In general, bolt holes spacing is 44mm using M4 bolt thread, same as for our motor mounts.
However, please be aware that the shaft as well as the motor pulley have to be of a very specific length / size in order to work with the Haggy Drive System.
If you intend to use your own motor, best is to get in touch with us and we will be happy to provide you the detailed requirements for shaft length and max. motor pulley size.