VESPA GTV 250 i.e. 2008 Service Station Manual page 130

Engine
- Calculate the clearance between valve and valve guide.
- Check that there are no signs of wear on the faying 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 MATING SURFACE, DO NOT ROTATE 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
Exhaust: 94.4 mm
Valve check: Standard length
Intake: 94.6 mm
Valve check Maximum admissible clearance
Exhaust: 0.072 mm
Valve check Maximum admissible clearance
Intake: 0.062 mm
Valve check standard clearance
Exhaust: 0.025 to 0.052 mm
Valve check standard clearance
Intake: 0.013 - 0.040 mm
Valve check Minimum admissible diameter:
Exhaust: 4.95 mm
Valve check Minimum admissible diameter:
Intake: 4.96 mm
Valve check Standard diameter:
Intake: 4.972 - 4.987 mm
Valve check Standard diameter:
Exhaust: 4.96 - 4.975 mm
ENG - 130
Vespa GTV 250 i.e.