Inspecting The Valves - Derbi GP1 125-250 c.c. Workshop Manual

I I
NSPECTING THE VALVES NSPECTING THE VALVES
- Check the valve stem diameter at the three points shown
in the figure.
- Calculate the clearance between valve and valve guide.
- Check that the contact surface with the articulated register
terminal is free from wear.
- If the checks above give no failures, you can use the same
valves. To obtain better sealing performance, grind the val-
ve. Perform this operation carefully using fine grain emery
paste. While grinding, keep the head with the valve axes in
horizontal position to prevent the emery paste residues from
penetrating into the valve guide stem coupling (see figure).
CAUTION
TO PREVENT SCRATCHING THE CONTACT SURFACE, DO NOT
FORCE THE VALVE ROTATION WHEN THE EMERY PASTE FINIS-
HES. CAREFULLY CLEAN THE HEAD AND THE VALVES USING
A SUITABLE PRODUCT FOR THE TYPE OF EMERY PASTE USED.
N.B.
DO NOT CHANGE THE VALVE ASSEMBLY POSITION.
Characteristic
Valve check: standard length
Exhaust: 94,4 mm
Valve check: standard length
Intake: 94,6 mm
Valve check: maximum admissible clearance
Exhaust: 0,072 mm
Valve check: maximum admissible clearance
Intake: 0,062 mm
Valve check: standard clearance
Exhaust: 0,025 ÷ 0,052 mm
Valve check: standard clearance
Intake: 0,013 ÷ 0,040 mm
Valve check: minimum admissible diameter
Exhaus: 4,95 mm
Valve check: minimum admissible diameter
Intake: 4,96 mm
Valve check: standard diameter
Intake: 4,972 ÷ 4,987 mm
Valve check: standard diameter
Exhaust: 4,96 ÷ 4,975 mm
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