BMW bikes engine ECU are few types – BMSK, BMSX, BMS2K or BMSMP:
For BMSKP ECU – keys are stored in ECU. Memory device is flash chip ST M58BW0160 – 80 pin PQFP package.
Expected file size is 2097152 bytes. Reading is thru BDM100 interface or with flash programmer.
For BMSX or BMS2K or BMSMP ECU – to see where keys are stored you must check what is on ignition barrel.
If there is IMMOBOX UNIT – keys are stored in this unit.To make key you need software 191
If there is KEY READER UNIT – keys are stored in ECU. Memory device is TRICORE MCU eeprom area.
Expected file size is 65536 or 196608 or 262144 bytes.

Use TMPro chip or PCF7936 or Silca T14 – JMA TP12 transponder.