2005 Yamaha F90TR 90HP Outboards Factory Service Manual, Page 78Get this manual
Power unit 11Remove the valve shim from the valve lifter using thin screwdriver19Check that the "TDC" mark on the flywheel magnet is aligned with the pointer b, and that" marks and on the driven sprockets are aligned c D
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12Measure the valve shim thickness with micrometer, and then note the measurement13Select the necessary valve shim by calculating its thickness with the following formulaNecessary valve shim thicknessRemoved valve shim thicknessMeasured valve clearance Specified valve clearance Example: If the "Removed valve shim thickness" is 2.10 mm, the "Measured valve clearance" is 0.30 mm and the "Specified valve clearance" is 0.20 mm, then the necessary valve shim thickness2.100.30 0.202.20 mm 14Install the necessary valve shim into the valve lifter, and then install the valve lifters into the cylinder head15Install the camshafts, camshaft caps, driven sprockets, and timing belt, and then tighten the tensioner bolt16Check the valve clearanceAdjust if necessary17Loosen the tensioner bolt, and then remove the timing belt and driven sprockets18Install the cylinder head cover and driven sprockets