PIAGGIO Beverly 250 USA Workshop Manual page 149

Beverly 250 USA
Engine
- Calculate the clearance between valve and valve guide.
- Check that there are no signs of wear on the surface of contact with the articulated register terminal.
- If the checks above give no failures, you can use the same valves. For best sealing results, it is
advisable to grind the valves. Grind the valves gently with a fine-grained lapping compound. During the
grinding, keep the cylinder head with the valve axes in a horizontal position. This will prevent the lapping
compound residues from penetrating between the valve stem and the guide (see figure).
CAUTION
TO AVOID SCORING THE FAYING SURFACE, DO NOT KEEP ROTATING THE VALVE WHEN NO
LAPPING COMPOUND IS LEFT. CAREFULLY WASH THE CYLINDER HEAD AND THE VALVES
WITH A SUITABLE PRODUCT FOR THE TYPE OF LAPPING COMPOUND BEING USED.
N.B.
DO NOT CHANGE THE POSITIONS THE VALVES ARE FITTED IN
Characteristic
Valve check standard length
Outlet: 94.4 mm
Valve check standard length
Inlet: 94.6 mm
Valve check Maximum admissible clearance
Outlet: 0.072 mm
Valve check Maximum admissible clearance
Inlet: 0.062 mm
Valve check standard clearance
Outlet: 0.025 ÷ 0.052 mm
Valve check standard clearance
Inlet: 0.013 ÷ 0.040 mm
Valve check Minimum admissible diameter
Outlet: 4.95 mm
Valve check Minimum admissible diameter
Inlet: 4.96 mm
Valve check Standard diameter:
Inlet: 4.972 ÷ 4.987 mm
Valve check Standard diameter:
Outlet: 4.96 ÷ 4.975 mm
ENG - 45