The lubricating oil should be drained out of the crank case every five hundred miles, and the case washed out with kerosene before refilling it with fresh oil. Gasoline has too great a cutting action to warrant its use for this, as it cleans down to the bare metal, while kerosene removes the dirt and grease, leaving a good surface. The case should be filled with oil to such a depth that the connecting rods will dip into it from a half-inch to an inch.
The same should be done with the change-speed gear case every thousand to fifteen hundred miles, for the particles of metal that will be ground from the gears will injure the teeth and bearings. In refilling, the smallest gear should project about an inch into the oil. If the differential is packed in grease, it will run for an entire season with one filling, but if it runs in oil it should be cleaned and washed two or three times a year. The bevel gear case of a shaft-driven car should receive the same attention.
CARE OF CHAINS
Properly lubricated chains should run for at least a thousand miles without attention. Because of their exposed position they should be protected against undue wear, and this is best attained by soaking them, when thoroughly cleaned, in melted tallow, working each joint in order that the liquid may penetrate. The chain should be hung up to cool and dry, the surplus tallow being wiped off. The hardened tallow in the joints will prevent grit from working in, and is a lubricant as well. To clean a chain, soak it in kerosene, working each joint to remove the grit. The stretching of the chain may be taken up by lengthening the radius rods, but when the stretching reaches a point that permits it, the chain should be shortened by the removal of a link, and the rods readjusted. If a complete chain is not carried as a spare part, the kit should always include a few extra links for emergency repairs. These are not difficult to apply, being secured in position by nuts instead of by burring over the ends of the rivets.
VALVE GRINDING
To grind a pitted or worn mechanically operated valve, the pressure should be released by compressing the spring and removing the key or other device by which it is held in place. On removing the plug over the valve pocket, the upper surface of the valve disk will be exposed, and it will be found to be provided with a slot. While many grinding pastes may be purchased, good results will be obtained by mixing machine oil with flour of emery until it is thick. Plugging the opening from the valve pocket to the combustion space with cotton waste to prevent the paste from entering the cylinder, spread it on the valve disk and seat, and rotate the disk on its seat with a screwdriver, preferably by means of a bit brace. Every little while the disk should be lifted and replaced on the seat in a new position, in order to distribute the wear evenly, and the grinding continued until a smooth surface shows all around both disk and seat. It is not necessary to smooth the entire surface of the disk and seat, for the pressure will be retained by a narrower surface.
An automatic valve may be removed from the cylinder by unscrewing or unbolting its cage, and after releasing the spring the cage may be held in a vise while the grinding is performed.
After grinding, all traces of the paste should be removed by washing with gasoline, for any particles that remain will cause rapid wear. When replacing the spring, that of the mechanically operated valve will be found difficult to compress to the point at which the key or washer may be slipped into position, and to simplify this many engines are built with a knob or boss on the cylinder to serve as a fulcrum by which a forked lever may be used. If this is not the case, the spring may be sufficiently compressed in a vise, and bound endwise with wire to retain it, the wire being cut when the spring and key are in position.
CARE OF STEERING MECHANISM
A failure of the steering mechanism will cause a wreck more surely and quickly than the breakdown of any other part of the car, and the best protection is absolute knowledge that it is in perfect condition. All joints should be kept well lubricated, and protected from dust; the leather protectors that are furnished do not accomplish this any too well, but they are much better than nothing, and if the joints are packed with grease before applying them, the results will be good. While guarding against stiffness, there should be very little play or lost motion in the mechanism, and the parts should be frequently examined for bent rods and loose joints. A bend in the drag link or steering knuckles will throw the front wheels out of true, in which case the tires will be badly worn. When going straight ahead, the wheels should be parallel; if this is the case, the angles of the steering arms will give the proper track when making a turn.