The Fuel Tank must be removed in order to check or reset the clearances. Undo and remove the nuts securing the two rocker covers and take off the one at the front over the exhaust rocker. The Inlet cover can only be raised upon its studs and cannot be taken off unless the cylinder head is off the engine or the engine is out of the frame.
Set the crankshaft with the piston at top dead centre of the compression stroke. This position can most conveniently be found by pressing down the footstarter until the resistance of compression is felt (open throttle and air controls fully to provide "something to compress" in the cylinder). Having found the compression stroke take out the sparking plug and insert a spoke or straight piece of stiff wire through the plug hole to feel the piston. DO NOT USE A SHORT LENGTH OF WIRE — IT MAY BE DROPPED ACCIDENTALLY INTO THE CYLINDER. Holding the wire carefully move the crankshaft forward slowly until the piston is felt to reach its highest point in the cylinder, i.e., top dead centre. Check clearances with a "feeler" gauge. Inlet should be .006-in., Exhaust .010-in.
If re-adjustment is needed, loosen the rocker pin locknuts with the spanner provided, and then turn the rocker pins to increase or decrease the clearance, whichever is needed. To increase the clearances turn the exhaust rocker pin anti-clockwise and the inlet pin clockwise. To decrease the clearances turn the exhaust rocker pin clockwise and the inlet anti-clockwise. If reference is made to the illustration on page 30 it will be seen that the "V" marks are moved upwards to increase, or downwards to decrease clearances.
Always check and reset clearances when engine is cold. Finally refit rocker covers with a light smear of Jointing compound on the joint faces and fit and tighten the nuts evenly.