VESPA ET4 50, Workshop Manual

Page: 92 / 185

5 +0+0.012mm
Intake guide: Wear limit
5.022 mm
- If the width of the impression on the valve seat or the diameter of the valve guide exceed the specified
limits, replace the cylinder head.
- Check width of the impression on the valve seat « V »
Characteristic
Wear limits:
Max. 1.6 mm.
Inspecting the valves
- Measure the diameter of the valve stems in the
three positions indicated in the diagram.
- Calculate the clearance between the valve and
the valve guide.
Characteristic
Minimum diameter allowed: Intake
4.970 mm
Minimum admissible diameter drainage
4.960 mm
Fitting clearance
Standard clearance: Intake
0.015 ÷ 0.042 mm
Standard clearance: drainage
0.025 ÷ 0.052 mm
- Check that there are no signs of wear on the
contact surface with the articulated register termi-
nal.
- If the sealing surface on the valves is wider than
the specified limit, damaged in one or more points
or curved, replace the valve with a new one.
Characteristic
Valve standard length: Intake
70.1 mm
Valve standard length: drainage
69.2 mm
Fitting clearance
Max. clearance allowed: Intake
0.052 mm
Max.
clearance allowed: drainage
0.062 mm
- If the checks above give no failures, you can use the same valves. For best sealing results, it is
advisable to grind the valves. Grind the valves gently with a fine-grained lapping compound. During
Engine
ET4 50
ENG - 92