.016 inch so that the tappets may be well clear of the quietening curves of the camshafts. The timing gears are marked to facilitate their replacement. To re-set the valve timing, by using the marks on the gears, proceed as follows;— Turn over, the engine till the mark on the small timing pinion is in line with the centre of the inlet (rear) camshaft bush. Insert the inlet camshaft so that the No. 2 or No. 3 mark on it is in mesh with the mark on the small timing pinion, according to model. Rotate the engine in a forward direction till the mark on the small timing pinion is in line with the centre of the exhaust (front) camshaft bush. Insert the exhaust camshaft so that the No. 1 mark on it is in mesh with the mark on the small timing pinion.
Trials Models Inlet opens 26° before top dead centre. Inlet closes 53° after bottom dead centre. Exhaust opens 64° before bottom dead centre. Exhaust closes 25° after top dead centre, taken with 0.016" tappet clearance and with the valve 0.001" off its seat.
ENGINE OVERHAUL 250 c.c. and 350 c.c- Lightweight Models
Removing the engine from frame. The engine with gear box can be removed as a complete unit—removing the gear box first makes handling easier. Disconnect battery wires as a precaution against fire. Start by stripping down as described for "removing the cylinder and piston". Remove drain plug from front chain case to drain oil. Remove near side footrest and engine plate cover—two screws. Remove four snap connectors on alternator cables. Remove six chain case screws and inspection cap. Remove chain case cover—with care to allow the cables to come through the rear portion of the case. Remove three clutch springs—take away the pressure plate. Remove gear box mainshaft nut securing clutch. Remove nut fixing rotor on engine shaft—use a close fitting ring spanner. When a duplex front chain is used remove the clutch and engine sprocket simultaneously as the chain is “endless”. When a single chain is used take out the connecting link. Remove three screws securing the rear portion of chaincase. Remove fairing for timing cover 042053/4, pull out the contact breaker wire. Removing the gear box. Remove connecting link from rear chain, take out the clutch cable. Remove kickstarter crank and gear pedal. Remove gear box adjuster bolt 042394 also all nuts fixing right side 35
