This is a quick tutorial on how to check, clean, control or refurbish a K bike fan. It had been written (in French) by Michel 09 a member of this French BMW Forum.
If you are removing your lower fairing, It is a good time to control the operation of the fan. A small check involves rotating blades with your fingers to assess its resistance (Everyone thinks differently of what the resistance should be, I would simply say that the fan must turn freely without force and without noise), otherwise it is likely that oxidation has made its way to the shaft and bushings.
1) Removing the fan support (everyone knows how to do ......!)
2) Remove the clips holding the plastic cover
3) After you unsoldered the 2 wires, carefully remove the lock washer with a
screwdriver (warning, below there are 2 fibre washers!)
The violet/yellow wire is the positive, the brown wire is the ground
4) Remove the clips maintaining the motor and remove it by pulling and giving
it a quarter turn movement
(Warning, when reassembling, correctly position the locating tabs - Picture on the right)
5) Place 2 wooden blocks under the blades, the drive shaft should come fairly easily, do not hit it too hard .....!
6) Depending on the condition, brush, clean, spray penetrating oil, and let it soak, (in my case I had to tap it (slowly) alternately from one side and the other to eventually loosen it. Once well cleaned, lightly oiled (no more than a ladle per bearing :-) ). At this stage you can easily rotate the shaft with your fingers.
7) Check the brushes, They should not be worn as the fan doesn't turn a lot. Be sure that all contacts are cleaned and the brushes are moving freely.
Little trick to finish, to put the springs in place using a small wire.
Your fan is now ready to be re-assembled.