Suzuki DF 25 Service Manual page 144

Valve stem end deflection
If unable to measure valve guide inside diameter, check "Valve
stem end deflection".
09900-20602 : Dial gauge
09900-20701 : Magnetic stand
Measure valve stem end deflection as follows:
(1) Install valve into valve guide.
(2) Position valve head at approx. 5mm away from valve seat.
(3) Move stem end in the directlon "X-Y", and measure deflec-
tion.
Valve stem end deflection
Service limit :
IN 0.14 mm (0.006 in.)
EX 0.18 mm (0.007 in.)
If measurement exceeds service limit, replace valve.
If measurement still exceeds service limit with newv alve, re-
place valve guide.
Valve stem end length
Inspect valve stem end face for pitting and wear.
If pitting or wear is found, valve stem end may be resurfaced.
Use caution when resurfacing, do not grind away stem end
chamfer.
When chamfer has been worn away, replace valve.
09900-20101 : Vernier calipers
Valve stem end length 1
Service limit :
IN 7.00 mm (0.276 in.)
EX 6.00 mm (0.236 in.)
POWER UNIT 7-27
X
Y