And here is the cut out in the nickel silver frame to take the XO-4 motor. There are a couple of soldered shims each side of the front bearing which hold the front of the motor in place (as well as the lugs at the base). The entire motor is held by the screw at the rear of the magnet. The gears meshed perfectly first time, with no adjustment necessary. I consider myself very lucky in this respect.

By adjusting the rear screw backward by about 1 mm I was able to fit the Airfix brushes just behind the rim of the center driver. (The old Triang brushes won't fit anyway.) This rear adjustment also solved a slight hesitation which I found was the axle gear rubbing against the front of the motor.

The motor is quite noisy after listening to the modern can motors with their faint whining, but that is to be expected.