BRP Johnson 4HP Service Manual page 88

POWERHEAD
VALVE / VALVE GUIDE
Valve stem runout
Measure the valve stem runout.
 Dial gauge
Magnetic stand
"V" block set
Valve stem runout:
Service limit: 0.05 mm (0.002 in)
If the measurement exceeds the service limit, replace the
valve.
Valve head radial runout
Measure the valve head radial runout.
 Dial gauge
Magnetic stand
"V" block set
Valve head radial runout:
Service limit: 0.08 mm (0.003 in)
If the measurement exceeds the service limit, replace the
valve.
Valve head thickness
Measure the thickness T of the valve head.
 Vernier calipers
Valve head thickness:
Standard:
IN 1.0 mm (0.04 in)
EX 1.0 mm (0.04 in)
Service limit:
IN 0.5 mm (0.02 in)
EX 0.5 mm (0.02 in)
If the measurement exceeds the service limit, replace the
valve.
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