Amazingly enough the toothed pulley unscrewed without any drama! You are correct when you say they are pretty sturdy. In my defence, I reckon most manufacturers would have pressed it on! Motors are throw away items these days. BUT I should have checked first.
Before I press the new bearing on, can I ask how you get at the bottom bearing for replacement? I THINK I know, but this time I am asking FIRST (breaking the habits of a lifetime!!). The bottom bearing feels good, but maybe I should replace it while I am at it.
The motor was the original one and I replaced it with a new one from yourselves, a year or three ago. It is in reasonable condition and simply needed the bearing change, so it is just a spare. Having had the X4 for well over 15 years, I am looking for a good few years more (Yes I am a cheapskate!).
Thanks for the help, the whistling emojo summed it up very well.