Things to remember though , is the motor one direction only or will it run the other way if you reverse the polarity , if not you will have to mount it on the other side of the chain ......also the chain length , can it easily be shortened , it may have a split link in it or you will have to get a link removal tool , halfords do them , prob £10 these days , if its bike chain style of course.
Just saving you unforseen probs old bean !