Ducati Diavel Workshop Manual page 706

Cylinder head assemblies: valves - rocker arms
Check the valve stem for buckling. Place it on a "V" block and measure deformation with a dial gauge.
Service limit: 0.053 mm.
Check the valve stem for buckling. Place valve on a "V" block, set a dial gauge perpendicular to head and measure run-
out of valve face at 45°.
- nominal concentricity: 0.01 mm;
- service limit: 0.03 mm.
Use Prussian blue or a mixture of minimum and oil to check that the contact surface (W) between the valve and seat is
1.4 to 1.6 mm (1.05 to 1.35 mm when new). Grind the seat if the dimension measured is greater than the above limit.
Checking the valve seal
After grinding the seats it is important to check the seal between the valve face and the seat: if the seat contact area (S)
on the valve is wider than the 45° band (W) this could lead to poor sealing.