Inspecting The Valves - PIAGGIO MSS Fly 50 4T Workshop Manual

MSS Fly 50 4T

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
Standard clearance: drainage
- 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
clearance allowed: drainage
- 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
grinding, keep the cylinder head in a horizontal position. This will prevent the lapping compound resi-
dues from penetrating between the valve stem/guide coupling.
CAUTION
TO AVOID SCORING THE CONTACT SURFACE, DO NOT KEEP ROTATING THE VALVE WHEN
NO LAPPING COMPOUND IS LEFT. CAREFULLY WASH THE CYLINDER HEAD AND THE
VALVES WITH A SUITABLE PRODUCT FOR THE TYPE OF LAPPING COMPOUND BEING USED.
0.015 ÷ 0.042 mm
0.025 ÷ 0.052 mm
Max.
0.052 mm
0.062 mm
Engine
ENG - 97