Yamaha SR400 2014 Service Manual

VALVES AND VALVE SPRINGS5-20TIPFor the best lapping results, lightly tap the valveseat while rotating the valve back and forth be-tween your hands.e. Apply a fine lapping compound to the valveface and repeat the above steps.f. After every lapping procedure, be sure toclean off all of the lapping compound from thevalve face and valve seat.g. Apply blue layout fluid “b” to the valve faces.h. Install the valve into the cylinder head.i. Press the valve through the valve guide andonto the valve seat to make a clear impres-sion.j. Measure the valve seat width “c” again. If thevalve seat width is out of specification, refaceand lap the valve seat.▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲EAS24310CHECKING THE VALVE SPRINGSThe following procedure applies to all of thevalve springs.1. Measure:• Valve spring free length “a”Out of specification  Replace the valvespring.2. Measure:• Compressed valve spring force “a”Out of specification  Replace the valvespring.Inner springFree length (intake)45.30 mm (1.78 in)Limit43.00 mm (1.69 in)Free length (exhaust)45.30 mm (1.78 in)Limit43.00 mm (1.69 in)Outer springFree length (intake)44.60 mm (1.76 in)Limit42.00 mm (1.65 in)Free length (exhaust)44.60 mm (1.76 in)Limit42.00 mm (1.65 in)a. Compressed valve spring forceb. Installed length