On emission controlled vehicles, the intake rocker arms have two valve clearance adjusting screw and one more of these screws is provided for the jet values. Before the intake valves there should be the jet valves on engines which have them; one should regulate them. To position the intake valves for clearance checking, free the locknut and turn the adjuster screw which regulates the intake valve on the first rocker-arm being worked on counterclockwise to two turns to ensure that there is no clash of the adjustment of the jet valve. Subsequent to this, loosen the locknut of the jet valve adjuster screw with your fingers and with the feeler blade, adjust the distance approximately between the extreme end of the screw and the valve stem then revert to tightening the locknut again without changing the position of the former screw. Adjust the intake valve clearance on this arm to standard and carry out the same on the other valve rocker arms rotating the
Crankshaft in order to set the intake valves at their correct clearance check position as well as setting the exhaust valve clearances at the same time. It is necessary to work intensely on these emission-controlled engines so that they do not cool, an action which will make the settings go off. If the jet valve clearance is not set properly it is likely that the engine will experience misfiring, poor performing engine and an incorrect exhaust gas content of CO.