PIAGGIO X9 Evolution 125 2008 Service Station Manual page 127

X9 Evolution 125
Inspecting the valves
- Measure the diameter of the valve stems in the
three positions indicated in the diagram.
- Calculate the clearance between valve and valve
guide.
- Check that there are no signs of wear on the fay-
ing surface with the articulated set screw terminal.
- If no anomalies are found during the above
checks, 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. Upon 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 COM-
POUND 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 FIT-
TED IN
Characteristic
Valve check Standard length
Exhaust: 94.4 mm
Valve check Standard length
Inlet: 94.6 mm
Valve check Maximum admissible clearance
Exhaust: 0.072 mm
Valve check Maximum admissible clearance
Inlet: 0.062 mm
Valve check standard clearance
Exhaust: 0.025 ÷ 0.052 mm
Valve check standard clearance
Inlet: 0.013 ÷ 0.040 mm
Valve check Minimum admissible diameter:
Exhaust: 4.95 mm
Valve check Minimum admissible diameter:
Engine
ENG - 127