Ducati MONSTER 821 Workshop Manual page 1110

Use a feeler gauge to check the clearance between the timing sensor (15) and the timing gear (23):
the value must be between 0.6 and 0.8 mm.
If previously disassembled, reassemble the oil vapour breather valve as follows:
Fit two new O-rings (11) after having lubricated them with the indicated product.
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