Nanni T4.155 seriers, Workshop Manual

Page: 104 / 191

60300140 (
indice A
) 4 CYLINDERS WORKSHOP MANUAL 104/191
4. CLEAN THE VALVES
a. Use a gasket scraper to separate any accumulation of carbon
deposits on the tops of valves.
b. Use a metal brush to carefully clean valves.
5. CHECK RODS AND VALVE GUIDES
a. Measure the inside diameter of each valve guide using a
micrometer.
Guide inside diameter: 8.010 – 8.030 mm
b. Use a micrometer to measure the diameter of valve stems.
Valve stem diameter:
Intake :
7.975 – 7.990 mm
Exhaust: 7.960 – 7.975 mm
c. Subtract the measured value for the valve stem guide from the
value of the external diameter of the valve guide bush.
Nominal oil clearance:
Intake:
0.020 – 0.055 mm
Exhaust: 0.035 – 0.070 mm
Oil clearance limit:
Intake: 0.08
mm
Exhaust: 0.10 mm
If the oil clearance is greater than the maximum limit, replace the valve
and the guide bush involved.