2005 Yamaha F90TR 90HP Outboards Factory Service Manual, Page 77Get this manual
Power unit Valve clearance (cold): Intake e: 0.20 0.03 mm (0.008 0.001 in) Exhaust f: 0.34 0.03 mm (0.013 0.001 in) 6Turn the flywheel magnet 360 clockwise7Check the intake valve clearance for cylinders #3 and #4, and the exhaust valve clearance for cylinders #2 and #4Adjust if out of specification8Turn the flywheel magnet clockwise and align the "TDC" mark on the flywheel magnet with the pointer, and check that the" marks on the driven sprockets are aligned9Loosen the tensioner bolt 7, and then remove the spring 8, timing belt 9, driven sprockets 0, camshaft caps A, and camshafts B