Suzuki DF25/DF30 Four Stroke Service Manual, Page 144Get this manual
POWER UNIT 7-27 Valve stem end deflection If unable to measure valve guide inside diameter, check "Valve stem end deflection"09900-20602Dial gauge 09900-20701Magnetic stand Measure valve stem end deflection as follows: (1) Install valve into valve guide(2) Position valve head at approx5mm away from valve seat(3) Move stem end in the directlon "X-Y", and measure deflectionValve stem end deflection Service limitIN 0.14 mm (0.006 in EX 0.18 mm (0.007 in If measurement exceeds service limit, replace valveIf measurement still exceeds service limit with newv alve, replace valve guide