The negative cable, which is normally connected to the negative pole of the battery, is fastened to the crankcase. From here, the cable branches off and splits up within the electrical system to carry the ground connection to the different elements in the system.

The image shows the ground connection on left side of the engine crankcase.
The battery charging circuit and power distribution
Electrical power for lighting and signalling devicesLimitations
This emission control system warranty shall not cover any
of the following:
Repair or replacement required as a result of
Accident,
Misuse,
Repairs improperly performed or replacements improperly
installed,
Use of replacement parts or accessories not conforming
to ducati specifi ...
Inspection of the gear selector drum
Use a gauge to measure the clearance between fork pin and the slot on the
selector drum.
If the service limit is exceeded, determine which part must be replaced by
comparing these dimensions with those of new
components (sect. 3 - 1.1, Gearbox).
Also check the wear on the drum support pin ...
Refitting the number plate holder
Place the number plate light (5), as indicated, on the number plate holder
plate (8) and tighten the screws (7) to a torque
of 2 nm +/- 10% (sect. 3 - 3, Frame torque settings).
Thread the number plate light wiring (c) into the opening in the number plate
holder plate as shown.
Fit ...