Sprocket carrier bearing swap

 The bearing required for this is a 17x40x12 and I used a 6203 2zz double shielded bearing.

To swap the bearing you need to strip the carrier which is made of three parts- the sprocket, the bearing plate and the drive plate. Remove the loose spacer and use circlip pliers to remove the circlip retaining the bearing.  

Remove circlip and spacer

Remove the sprocket by removing the 3 14mm nuts and their spring washers

Remove the 3 14mm nuts and lift off the sprocket.

Lift off the sprocket here the upper view shows the bearing carrier plate which is penetrated by the three sprocket mounting studs from the drive plate beneath.

Sprocket carrier- bearing plate side

Whilst the rear shows the base of the drive plate with the three drive transmitting studs that engage with the hub.

Sprocket carrier drive transmission side.

The two sections just pull apart.

Sprocket carrier separated showing rear of bearing plate.

A second view shows the exterior side of the bearing plate with stub axle protruding. 

Sprocket carrier separated showing front of bearing plate.

Note that the bearing is inserted into the bearing plate from the front  until it rests against the flange at the base of its socket.  To remove a bearing from a socket you would normally press it out by pressing against the outer race only. However in this case that isn't possible because the outer race is now hidden by the flange at the base of the socket.

Rear of bearing plate

There is no option but to press it out using the base of the stub axle which of course will bear on the inner race of the bearing. This will almost certainly damage the bearing but as I'm intending to change it anyway I guess in this case it doesn't matter! I used a double socket arrangement in the vice- the smaller socket pushes on the rear of the stub axle, whilst the larger surrounds the bearing, pressing on the front of the plate, and is deep enough to accept the bearing as it moves outwards.

Pressing out the old bearing

The old bearing is pressed out together with the stub axle.

Bearing removed

The stub axle is inserted from the other direction, the flange of the stub  axle resting against the rear of the bearing. To remove this its necessary firstly to protect it. I refitted the stub axle nut flush with the end of the stub to avoid thread damage.

Socket arrangement to press out stub axle

I then selected a socket large enough to press on the bearing outer race and used the vice to press the stub axle out of the centre of the bearing. This worked well and the extracted stub axle is shown below.

Stub axle removed

Clean all recesses and the inserts then start to fit the new bearing by hand. Once it started to bite I used the old bearing as a drift to tap it into the recess until it bottomed out on the flange and exposed the upper circlip groove. I then cleaned and refitted the circlip. 

The stub axle was then pressed into the base of the bearing from the other side using the vice against the base of the stub axle and a deep socket on the other side; large enough to rest on the bearing inner race, and deep enough to accept the stub axle as it emerged through the bearing. 

Stub axle inserted into new bearing

Bearing plate reassembled

The carrier was then reassembled by reversing the above process.