VALVE TIMING

In many cases where engine is hard to start, trouble can he traced to the valves not being timed properly.

As this is a four cycle engine, we will show you the four distinct parts in the movement of the piston and crankshaft and the timing of the valves.

The first is known as the suction stroke, during which time the piston is traveling from extreme inner to extreme outer position, causing a vacuum which automatically opens the inlet valve and admits a charge of kerosene mixed with air from the carburetor.

In the next or compression stroke, the piston returns from extreme outer to extreme inner position, compressing the charge which has been drawn into the cylinder. During this stroke both valves remain closed. The spark taking place just before the end of this stroke.

The third, or power stroke, is caused by the force of the explosion in the cylinder driving the piston out again to its outer position. Before the piston reaches the extreme Outer position the exhaust valve is opened by means of a cam which pushes out the cam rod and works the valve lever and lifts the valve. The proper time for this valve to start to lift is when the crankshaft is half way between the vertical and horizontal position on the downward part of this stroke.

We now come to the last or exhaust stroke. The exhaust is already open so as piston returns from its outer position it drives the burnt gases out into the exhaust pipe. The exhaust valve remains open until the crankshaft has passed the inner center 3° or 5° .

This adjustment is controlled by means of No. 06 adjustment screw (page 32), and is easily regulated.

Notice the setting of this valve from time to time, as this may work out of adjustment as the engine is used.

If exhaust valve spring has weakened to such an extent that suction is pulling in exhaust valve, replace with new spring.

When cam rod is not in contact with No. 06 adjusting screw, the No.24 valve lock lever should not bind on either valve stem. This can be easily regulated by readjusting the "C" valve lock stud. See illustration on opposite page, also page 31, Figure 11, for valve timing.

When an inlet or exhaust valve leaks, remove the cylinder head, take off the valve springs, remove the valve you want to grind and wash it and the valve seat in gasoline, then make a paste of fine emery dust and oil. If you cannot get emery dust, use powdered pumice stone with oil. (You can get powdered pumice stone at almost any drug store.) Smear this on the valve and valve seat, put the valve in place and put a rail through the hole in valve stem on the outside of the head, grasp the nail with your fingers and turn from left to right for a minute or so, then lift the valve and turn it about half way around and repeat this until the valve and valve seat show an even surface all the way round.