To adjust the valve clearances, first set the no. 1
Piston at TDC on its compression stroke after removing the spark plugs by turning the
Crankshaft with a spanner until compression is felt at the no. 1 plug hole, then align the second mark on the crankshaft pulley with the
Timing Cover pointer. Adjust the two valve clearances nearest the front of the engine, where the left-hand valves are inlet and the right-hand valves are exhaust, both requiring a clearance between 0.006 and 0.008 in (0.15 to 0.20 mm). To adjust the gap, release the locknut on the
Rocker Arm, insert a thin rod into one of the holes in the eccentric cam, and turn the cam until the appropriate feeler gauge fits snugly between the cam and the valve stem, ensuring not to check the clearance between the rocker arm slide pads and the camshaft lobes. Retighten the locknut without moving the eccentric cam, then turn the crankshaft pulley nut until the no. 3 piston is at TDC, indicated by the downward-pointing high points of the no. 3 camshaft lobes, and check the clearances of the no. 3 valves. Repeat this process for the no. 4 valves when the high points of the no. 4 camshaft lobes are down, and then for the no. 2 valves when the high points of the no. 2 camshaft lobes are down, following the firing order to minimize unnecessary crankshaft rotation. Finally, check all rocker adjuster locknuts, remove the spanner from the crankshaft, and install the rocker cover with a new gasket, rechecking the valve clearances after 600 miles (1000 km).