- 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
unit.
Inspecting the valve sealings
- Measure the width of the sealing surface on the valve seats.
VALVE SEAL SURFACE
Specification Desc./Quantity
Intake valve - seal surface 2.4 to 2.8 mm
Exhaust valve - seal surface 2.2 to 2.6 mm
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
Standard drainage guide diameter
5.012 mm
Standard inlet guide diameter
5.012 mm
Vespa LX 125 - 150 i.e. Engine
ENG - 121