Note. For reasons of clarity, the figures show the cylinder head removed from the engine.
Remove the spark plugs so that it easier to turn the crankshaft.
Move the piston to TDC at the end of the compression stroke. In this position the two opening (upper) rockers are free.
Look through the hole in the alternator cover and check that the mark on the flywheel is aligned with the mark on the cover. Carry out this check for each cylinder.
Remove the inspection cover. Using a feeler gauge check the clearance between the opening (upper) rocker and the opening adjuster.
Using a screwdriver, push against the closing (lower) rocker to counteract the pressure of the return spring. Using a feeler gauge, check the clearance between the rocker and the return spring cap.
If the clearances measured are outside the specified limits, adjust following the instructions in the section below.