Yamaha F150A Service Manual

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7-41Cylinder head012345678910AChecking the cylinder head1. Remove carbon deposits from the com-bustion chambers, and then check thecylinder head for damage and scratches.2. Check the cylinder head warpage using astraightedge “1” and a thickness gauge“2” in 7 directions. Replace the cylinderhead if above specification.Checking the valve spring1. Measure the valve spring free length “a”.2. Measure the valve spring tilt “a”. Replaceif above specification.Checking the valve1. Check the valve face. Replace if pitted orworn.2. Measure the valve margin thickness “a”.3. Measure the valve stem diameter “a”.Cylinder head warpage limit:0.10 mm (0.0039 in)Valve spring free length “a”:48.08 mm (1.8929 in)21aValve spring tilt limit “a”:1.7 mm (0.07 in)Valve margin thickness “a”:Intake:0.40–0.80 mm (0.0157–0.0315 in)Exhaust:0.80–1.20 mm (0.0315–0.0472 in)aaa