Remove Commando Gearbox

Article by Mark Trotta

This article details how to remove a Norton Commando gearbox without removing the gearbox cradle.

NOTE: All Commando's prior to Mk3 models have the same cradle (06-4060). Mk3 models have a different cradle (06-5140) which do not provide enough clearance.

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To quote the factory service manual:

...remove the rear three crankcase bolts (or studs, depending on year), the rear wheel and on 1971 and later models, support the motorcycle by the lower frame rails on a strong box and remove the centre stand."

However, supporting the motorcycle and removing the rear wheel is not necessary on Mk2 and earlier models.

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With Engine Still In Frame

Exhaust system, kickstart lever, foot pegs, shifter, gear selector, and clutch cable all need to be taken off.

Unbolt left and right side Z-plates.

On my 1974 850 Roadster, there were seven tabs and brackets that needed to be unfastened to take out the battery box.

The spin-on oil filter and hoses will interfere, so they need to come off.

Clutch removal is covered here.

Removal of stator and rotor, primary chain, engine sprocket, clutch, chain-wheel, and chain-case is covered here

Primary chain, engine sprocket, and chain-wheel come off together.

The rear engine mounting bolts in the front of the cradle can stay.

NOTE: Draining the gearbox oil will be easier while it's still on the bike.

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With Engine Out Of Frame

After removing the engine from the frame of my 1974 Mk2 Roadster, these were the final steps before removing the gearbox:

First, an 8" x 6" x 6" block of wood was placed underneath for support. This bike has a side stand which was left in place, if yours has a center stand, it will need to be removed.

On the bottom of the cradle is the gearbox pivot stud (06-0597). It is 1/2" UNF X 5" with nuts and flat washers on both sides. Once one of the nuts is removed, use a punch and hammer to knock the stud through to the other side.

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On the upper right is the top mount bolt (06-2653). It goes through the gearbox adjuster and cradle, and attaches on the left side with a spacer (03-0023) and special nut (06-2656). I removed it with a 7/16 Whitworth socket.