79.6 mm
- If the checks above give no failures, you can use
the same valves. For best sealing results, it is ad-
visable to grind the valves. Grind the valves gently
with a fine-grained lapping compound. 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 to 34.4 mm
Vespa LX 125 - 150 i.e. Engine
ENG - 123
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