Ducati MONSTER 821 Workshop Manual page 967

Opening shims
Reset the dial gauge (C) and position stylus (D) on surface (G) of inspection gauge (F).
Insert the opening shim (6) fully against the inspection gauge, as shown in the figure.
Measure the shim thickness by placing dial gauge stylus on the shim surface.
Rotate the shim to take the measurement on different points. The difference between the thicker and the
thinner part must not exceed 0.02 mm.
Carefully clean the two intake valve seats (A) and the two exhaust valve seats (B).
Lubricate the stems of the two intake valves (7) and the two exhaust valve stems (8) with engine oil.
Fit the valves in their seats on cylinder head, fully home.
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