VESPA LX 150 4T Euro 3 Service Station Manual page 106

Engine
79.6 mm
- If no faults are found during the above checks,
you can use the same valves. For best sealing re-
sults, it is advisable to grind the valves. Grind the
valves gently with a fine-grained lapping com-
pound. During grinding, keep the cylinder head in
a horizontal position. This will prevent the lapping
compound residues from penetrating between the
valve stem/guide coupling.
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.
- Insert the valves into the cylinder head.
- Test the 2 valves alternatively.
- The test is carried out by filling the manifold with
petrol and checking that the head does not ooze
through the valves when these are just pressed
with the fingers.
Inspecting the springs and half-cones
- Check that the upper spring caps and the cotter
halves show no signs of abnormal wear.
- Check the unloaded springs length.
Characteristic
Valve spring length
33.9 - 34.4 mm
ENG - 106
Vespa LX 125 - 150 4T Euro 3