VESPA LX 4T USA Workshop Manual page 94

Engine
- Remove the central screw and the tensioner
spring. Check that the one-way mechanism is not
worn.
- Check the condition of the tensioner spring.
- If examples of wear are found, replace the whole
assembly.
Inspecting the valve sealings
- Measure the width of the sealing surface on the
valve seats.
Characteristic
Sealing surface width: Intake
1.5 mm
Sealing surface width: Drainage
1.6 mm
- 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 valve housings
- Remove any carbon formation from the valve
guides.
- Measure the inside diameter of each valve guide.
- Take the measurement at three different heights
in the rocker arm push direction.
Characteristic
Discharge guide: Standard diameter
5 +0+0.012mm
Discharge guide: Wear limit
5.022 mm
Intake guide: Standard diameter
ENG - 94
LX 4T USA