Suzuki DF 40 Service Manual page 175

Valve stem runout
Measure valve stem runout.
09900-20606 : Dial gauge
09900-20701 : Magnetic stand
09900-21304 : "V" block set
Valve stem runout
Service limit : 0.05 mm (0.0020 in.)
If measurement exceeds service limit, replace valve.
Valve head radial runout
Measure valve head radial runout.
09900-20606 : Dial gauge
09900-20701 : Magnetic stand
09900-21304 : "V" block set
Valve head radial runout
service limit : 0.08 mm (0.0031 in.)
If measurement exceeds service limit, replace valve.
Valve head thickness
Measure thickness of valve head.
09900-20101 : Vernier calipers
Valve head thickness
Standard :
IN 1.0 mm (0.0394 in.)
EX 1.15 mm (0.0453 in.)
Service limit :
IN 0.7 mm (0.0276 in.)
EX 0.5 mm (0.0197 in.)
If measurement exceeds service limit, replace valve.
POWER UNIT 6-32
45°