VESPA ET4 50, Workshop Manual

Page: 90 / 185

The procedure is different from that indicated in the vehicle manuals:
Head nuts tightening (only for stud bolts replacement) 6÷7 N*m +90° + 90° + 90°
The 45° rotation reduction of the key is necessary to avoid stud bolt stretching.
Inspecting the cylinder head
- Using a trued bar check that the cylinder head
surface is not worn or distorted.
- Check that the camshaft and rocking lever pin
bearings show no signs of wear.
- Check that the cylinder head cover surface, the
intake manifold and the exhaust manifold are not
worn.
Characteristic
Maximum admitted unevenness: Head check
0.05 mm
HEAD CHECK
Specification Desc./Quantity
Standard diameter (mm) A Ø 32.015 ÷ 32.025 mm
Standard diameter (mm) B Ø 16.0 ÷ 16.018
Standard diameter (mm) C Ø 11.0 ÷ 11.018
Inspecting the timing system components
- Check that the guide shoe and the tensioner shoe
are not worn out.
- Ensure that the camshaft drive pulley, the chain
assembly and the sprocket wheel are not worn.
- If sings of wear are found, replace the parts. if the
chain, pinion or pulley are worn, replace the whole
assembly.
Engine
ET4 50
ENG - 90