of the sleeve valve mechanism the views at Fig. 156 are presented. At A, the cylinder heads which have just been removed from the cylinder block B, are depicted. The connecting rod, piston and the two sleeve valves in one assembly just as it is removed from

the cylinder interior is shown at C. The piston and connecting rod removed from the interior of the inside or long sleeve is shown at B, the inside or long sleeve is outlined at E, and the short sleeve is shown at F. It will be apparent that the gas passages which are in the form of slots cut into the upper portion of the sleeve walls are not apt to change in size except the very small amount due to the deposit of carbon in the port openings. Obviously they may be restored to full size by scraping away that material.

The illustrations at Fig. 157 will show clearly the relation of the two sleeves and the cranks operating them, while the series of views at the right will show the way the various ports register

to provide a clear passage for the ingress or egress of the gases. At A, the piston is shown at top center, the exhaust ports have just closed and the inlet ports are just about to register and permit the gas to flow into the cylinder as the piston descends on its suction

stroke. At B, the piston is seen nearing the end of its stroke and the inlet port is fully open. The exhaust port is completely closed. At C, is shown the end of the intake stroke with the inlet ports just closing. The view at D, shows the piston at the end of its compression stroke with both inlet and exhaust ports closed. At E, the piston has gone down the greater portion of its power stroke and the exhaust openings in the inlet and outer sleeves are just beginning to meet and register with the exhaust outlet port in the cylinder. At F, the exhaust port is about half open, at G, the exhaust port is fully open. The piston and crank position at H, indicate the closing of the exhaust port. The inner and outer sleeves therefore, cannot vary in timing which is determined by the disposition of the throws on the sleeve operating crankshaft. If for any reason the proper relation of rotation between the main crankshaft and the member operating the sleeve valves is lost one may begin at cylinder No. 1 and time the engine in somewhat the same

manner as the poppet valve motor is timed. The instructions given for setting the sleeve valve of the Lyons-Knight motor are: the intake opens 10 degrees after top dead center and closes 40 degrees after the bottom dead center. The exhaust valve opens 60 degrees crank travel before the piston reaches the end of its power stroke and closes on dead center.

One peculiar point about the sleeve valve motor in which it differs radically from the poppet valve type is that the carbon deposits which are very detrimental to proper poppet valve operation are said to be actually beneficial to the operation of sleeve. valves because the carbon on the sleeves has a certain lubricating value. Instead of endeavoring to prevent carbon accumulation all sorts of expedients are tried in the various plants where sleeve valve motors are manufactured to assist carbon accumulation. Mr. Charles Y. Knight the inventor of this type of motor writes as follows regarding the formation and utility of carbon in sleeve valve motor operation:

"Providence seems in the case of the sleeve valve to deposit the carbon just where it is required, rectifying any small errors in clearances or adjustments or small ring leakages which may have crept into the construction. And the user is advised to be most careful about its removal-not to interfere with the deposit unless through some extraordinary conditions the character of the accumulation partakes of the scale-like formation which upon severe use of the motor becomes incandescent, as shown by its brown color and projecting scale-like form. Happily, such scale is seldom encountered, and when it may have formed as a result of the cause described, the user is advised to remove it, not with the use of a sharp-edged metal tool, but by employing a coarse, rough piece of fabric, which when rubbed heavily upon the surface to be cleaned, will serve to carry away the loose flakes, which could possibly cause self-ignition, without exposing the polished surfaces. of the head and piston. A carbon deposit upon the cylinder head rarely takes the form of scales because of its perfect cooling.

"My observation leads me to believe that the tendency to carbonize is growing with the lowering in the grade of the petrol supplied for fuel purposes. In short, it is my experience, sup