VESPA GTS Super 125 i.e., Service Station Manual

Page: 27 / 285

- If no anomalies are found during the above
checks, you can use the same valves. To obtain
better sealing performance, grind the valve seats.
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 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.
CAUTION
DO NOT REVERSE THE FITTING POSITIONS OF THE VALVES (RIGHT - LEFT).
- Check that the camshaft bearings exhibit no scores or abnormal wear.
- Using a micrometer, measure the camshaft bearings.
STANDARD DIAMETER
Specification Desc./Quantity
Bearing A Ø: 37 - 0.025 -0.050 mm
Bearing B diameter: 19 - 0.020 -0.041 mm
MINIMUM ADMISSIBLE DIAMETER
Specification Desc./Quantity
Bearing A Ø: 36.940 mm
Bearing B diameter: 19.950 mm
Vespa GTS Super 125 i.e.
Characteristics
CHAR - 27