Fein KBH 25 Repair Manual page 34

Insert field coil up to stop in motor housing –
the engraved serial number must be on the top of the motor housing (speed level for electronics)
Attach air guide ring and screw down in motor housing along with field coil
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FEIN REPAIR TOOLS
5.5. Fitting the motor
C-SC_CSSM 2012.05
Tool:
- Torx 20 screwdriver
- Plastic hammer