PIAGGIO 633929(IT), Service Station Manual, Page: 134 / 314

Inspecting the valve housings
- Check the width of the imprint on the valve
seat« V » wear limit max. 1.6 mm.
- 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.
- If the width of the impression on the valve seat or
the diameter of the valve guide exceed the speci-
fied limits, replace the cylinder head.
Characteristic
Valve seat wear Intake guide
limit accepted: 5.022
Valve seat wear Intake guide
Standard diameter: 5.000 ÷ 5.012 mm
Valve seat wear Exhaust guide
Accepted limit 5.022
Valve seat wear Exhaust guide
Standard diameter: 5.000 ÷ 5.012 mm
Inspecting the valves
- Measure the diameter of the valve stems in the
three positions indicated in the diagram.
- Calculate the clearance between valve and valve
guide.
- Check that there are no signs of wear on the sur-
face of contact with the articulated register termi-
nal.
- 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 the
grinding, keep the cylinder head with the valve ax-
es in a horizontal position. This will prevent the
lapping compound residues from penetrating be-
tween the valve stem and the guide (see figure).
Engine
MP3 125
ENG - 40