1996-2005 Suzuki DF40, DF50 Four Stroke Outboard Service Manual, Page 174Get this manual
6-31 POWER UNIT 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 direction "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 new valve, replace valve guideValve stem end length Inspect valve stem end face for pitting and wearIf pitting or wear is found, valve stem end may be resurfacedUse caution when resurfacing, do not grind away stem end chamferWhen chamfer has been worn away, replace valve09900-20101Vernier calipers Valve stem end length Service limit3.20 mm (0.126 in