How to video

Bosch bearing replacement guide

 

COMPONENTS
1. Crank shaft
2. Reduction gears
3. Idler gear
4. Security nut for torque sensor
5. Main motor drive gear and clutch bearing assembly
6. Left-hand crankshaft bearing
7. Left-hand outer crank arm circlip
8. Right-hand outer crank arm circlip
9. Crankshaft gear circlip (not necessary to remove)
10. Left hand crank shaft bearing circlip
11. Transfer gear from motor to main motor drive assembly
12. Circuit board screws
13. Right hand cover screws
14. Right hand motor cover

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1.
Remove both crank arms and plastic motor outer covers, next remove both crank arm cir clips from the crank shaft.

 

 

 

 

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2.
Remove the 6 x T25 Torx screws from the right-hand
motor cover.

 

 

 

 

 

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3.
Gently tap around the outside edge of the motor casing to break the seal.

(Don’t worry there is no gasket just a thin re-usable seal bonded to the cover)

 

 

 

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4.
You will probably have to drift the main motor drive gear and clutch bearing assembly out of the motor cover.

(Use a soft hammer or lump of wood between your hammer and the drive gear to avoid any damage.)

 

 

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5.
Press or knock the main motor bearing from the housing with a hammer and punch or similar.

 

 

 

 

 

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6.
Remove the transfer gear (No 11) from its locating pin

(if it doesn’t come off during Step 3)

 

 

 

 

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7.
Remove the wiring plugs from the sockets on the left-hand
side of the engine.

(This will aid moving the circuit board later on).

 

 

 

 

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8.
Bosch fit a security nut to hold the torque/movement sensor.

This MUST be removed.

If you don’t have a specialist tool, you can use a punch or chisel to loosen the nut. It can be replaced by a nice 10 x 1.5mm threaded lock-nut.

 

 

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9.
Remove the 6 T15 torx screws from the printed circuit board (PCB) and gently pry it away from the motor

(It is stuck by a few blobs of silicone).

DON’T pull it away to far!

 

 

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10.
Gently move the PCB up and out the way.

 

 

 

 

 

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11.
Remove the torque/movement sensor.

 

 

 

 

 

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12.
The reduction gears (No2) and the crank shaft gear will all come out together when you knock the crank shaft out of the left-hand crankshaft bearing

(use a soft hammer or block of wood to avoid damaging the shaft).

Keep an eye on the PCB too!

 

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13.
You can now access the left-hand crank shaft bearing (No 6) and cir-clip (No 10).

Remove this cir-clip and knock
the bearing into the motor area from the left-hand side.

 

 

 

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14.
Once the new bearing has been fitted the crank shaft and reduction gears must all go back in as an assembly.

Tap the crank shaft into the new bearing and replace the torque/movement sensor.

 

 

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15.
When replacing the PCB, take note of the exact wiring route for the torque/movement sensor wires.

 

 

 

 

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16.
Here I am using a 10 x 1.50mm lock nut which replaces the Bosch security nut.

 

 

 

 

 

 

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17.
It’s up to you but the right-hand crank bearing would be only replaceable with specialised equipment and a lot of finger crossing so I tend to pack this bearing with silicone grease on a regular basis to extend its life as
far as possible.

(I am working on a solution for the right-hand bearing replacement, so bear with me).

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18.
Replace both left and right crank arm cir-clips.

 

 

 

 

 

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19.
Use plenty of silicone grease around the main motor bearing, fit or refit the dust seal.

 

 

 

 

 

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20.
Refit your sprocket, O-ring and crank arms.

 

 

 

 

 

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21.
Job done and we didn’t even remove the motor!

 

 

 

 

 

 

Please note this is provided as a guide only for information purposes. I will not be responsible if you follow them and break something you will be doing so at your own risk!

Click the link below for a full downloadable replacement guide.

Bosch Performance Line Bearing Change

SES sprocket bearing change with tips