To insure a good seat to the valves when the stems are expanded by heat the stems should clear the set-screws on the levers at least ¹/₁₆ inch when the air and the exhaust levers are clear of the cams. A greater clearance is undesirable, as it prevents the full opening of the valves. If at any time the air-inlet or the exhaust valves appear to be opening or closing at the wrong time, take off the nut on the end of the lay shaft which holds the skew-wheel on and see that the chisel cuts on the shaft are opposite to one another. The lay shaft is coned where the skew wheel is fixed on and it is held on simply by friction, the nut being tightened against it. Should it at any time become necessary to take out the crank shaft, always be sure that the skew-wheel gearing is put together so that the tooth marked “0” on the crank shaft skew-wheel fits in between the two teeth marked “0” on the oil-shaft skew-wheel. =Vaporizer valve box and pipes attached to vaporizer.=—In this box there are two valves. The vertical one is regulated by the governor, and when the engine runs faster than its proper speed the governor pushes it down, thus opening it and allowing some oil to return to the oil tank. The horizontal valve in this box is a back-pressure valve. If at any time this valve is not working properly, vapor will be seen coming out of the overflow pipe; in this case the valve should be examined. By screwing off the outside cap the tail of this valve can be seen; if the valve is turned around a few times it will probably dislodge any dirt that may be under it; if, however, this does not stop the leakage the valve should be taken out for inspection. If the horizontal valve and sleeves are taken out at any time, great care must be taken in replacing them to use the same thickness of jointing material as before or the distance the valve opens will be altered. See that the pipe from the pump to the vaporizer valve box is inclined upward all the way from the pump. If this is not so, an air pocket will be formed in which a certain amount of air will be compressed upon each stroke of the pump. This will cause the oil to flow in slowly and not suddenly as it should. If the oil tank be emptied of oil at any time, air will get into the suction and delivery pipes of the pump and it will take some time before the oil going through the pump and pipes will be free of this air; for awhile thereafter, the engine will not work properly, as the air, by being compressed as the pump works, will interfere with oil being pumped in suddenly. It is best, if the oil gets below the filter in the tank, to work the pump by hand for about 10 minutes, holding the relief valve (on the vaporizer box) so as to get air well out of the pipes. =To stop the engine.=—Turn the crutch-handle regulator to “Shut.” Close the automatic lubricator. If it is desired to stop the engine for a short time only, put the lamp back under the vaporizer to keep it hot.