PUTTING IT BACK TOGETHER

Fit rear bearing

Support the rotor on the open jaws of a vice. Press the rear bearing onto the shaft with a socket – or carefully tap it on with a hammer and socket. Press on the inner track of the bearing only.

Fit front bearing

Press or tap the front bearing into the casing with a socket that bears on the outer track only. Or, if you warm the casing to about 80° in an oven, the cold bearing should simply drop straight in.

Screw on retainer

Refit the retainer plate. If it was originally riveted, replace them with setscrews and nuts. We’re upgrading to sealed (2RS) bearings with C3 clearance for engine-temperature use.

Press in rotor

Fit the rotor by tapping or pressing it into the front bearing. Ours was an overly tight fit, almost destroying the casing on removal. We carefully rubbed the shaft down until it was merely snug.

Reassemble casing

Remove corrosion from all mating faces and shoulders of the casings and stator. Lightly smear with copper grease. Get the front and rear pivot lugs in-line and press the halves together by hand.

Tighten screws

Tap around with a mallet to make sure everything’s seated squarely, then refit the screws. Apply a thin layer of copper grease along the whole length of the screws. Draw each up a little at a time. Refit brush unit

Slide the brushes in over a strip of folded paper or card. This prevents them from springing out, jamming or going cockeyed. Pull the card out only after you’ve got both screws loosely in place.

Check regulator earth

Screw the brush unit down. If it has a built-in regulator, make sure it can make a good earth with the casing. Some have an internal spring-loaded contact, too. Check that it’s in good condition.

Complete the unit

Refit the Woodruff key, fan, pulley and spring washer. Nip up the nut, clamping the pulley in a vice with a section of old fan belt as you did on disassembly. Don’t overtighten the nut.