the tappet or rod should be filed off until about 1/32 of an inch is left between the end of the valve stem and the push-rod or tappet. Never file off the end of the valve stem, as in this case a new valve will prove too long when placed in the old seat. New valves should always be ground into the seats, and a newly ground valve will never be quite tight until it has been operated for some time.

Emery and oil is an excellent grinding compound, but Tripoli, rotten-stone, or very fine pumice will give a smoother and more beautiful finish, although the grinding will take longer with these materials than with emery. Various valve-grinding compounds are on the market; and some of these that are composed of carborundum, and come in the form of a paste in collapsible tubes, are the finest and handiest of preparations for grinding valves. Being in a tight tube and already mixed, there is no danger of foreign matter or grit getting in and the consistency of the compound always remains the same. A tube of this material should be in the kit of every user of a four-cycle motor.

Even when the valves are well ground in and perfectly adjusted a motor will sometimes lose compression and yet it will be next to impossible to discover the joint or crack where the trouble occurs. At such times the leak may be readily located by squirting soapsuds around each joint while the motor is running. Wherever a leak occurs the suds will form bubbles and you will often be surprised to find how many unsuspected leaks there are in your motor when you test it by this method.

A great deal of valve trouble may be avoided by

placing a small ball race or thrust between the spring and valve foot as shown in Fig. 146. When this is done the valve revolves slightly each time it seats, and is thus continually resting on a new spot, causing less wear and liability to cut or pit.

A great many compression leaks may be traced to the priming or relief cocks. These cocks become exceedingly hot through their direct connection with the interior of the firing chamber and are therefore subject to very severe conditions. In order to be gas-tight they are provided with a stiff spring to hold the conical valve in position, and the heat frequently destroys the temper of this spring and allows the valve to shake loose. Oil and gasolene also tend to Fig. 146.-Valve gum up the cock and prevent it shutting gas-tight, and often the cock will leak considerably without visible evidence. A cock manufactured by the Morgan Mfg. Co. of Newport, R. I., and designed to overcome the many difficulties of spring seating cocks, is illustrated in Fig. 147. This is a distinct advance in this line of accessories and is a good illustration of how little things can be improved to add greatly to the efficiency and service of a motor.

with Ball-race

Many motor troubles are caused by an accumulation of soot and carbon in the cylinders, firing chamber, valve chambers, or one of the spark plugs or sparking electrodes. The quickest method of removing such deposits is by using one of the various carbon-removers

on the market. Care should be taken in using these to see that none of the compound is left in the motor or the crank case, as they will injure the engine unless thoroughly removed and the parts well oiled afterward. Only light deposits and gummed oil can be thoroughly removed in this way, and for such accumulations plain kerosene oil will work almost as well and is safer and cheaper. Where the deposits have become thick and

I

Fig. 147. "Morgan" Priming-cup

hard they must be removed by scraping and to do this the cylinder head and other parts must be removed. To thoroughly clean the carbon deposits from a neglected motor is a disagreeable, dirty, and tiresome job; but with decent care and attention there is no need of ever being obliged to do it. Good oil, and not too much of it, will prevent carbon from forming; and if once in a while the cylinders are wiped out with kerosene, and the spark plugs and valves cleaned, there will be no danger of being troubled with carbon and soot.

In removing piston rings great care should be used, as

these are very brittle and break easily. By spreading the rings slightly with a pair of pliers, as shown in Fig. 148, and then inserting strips of thin tin or brass beneath them, they will slip off easily (Fig. 149); new rings should be put on in the same way. The last or lowest ring should be taken off first and the others in

Fig. 148. Spreading

Rings with Pliers

Fig. 149.-Shims for
Removing Rings

regular order, and in replacing them the reverse order should be followed, as otherwise the rings will slip into the empty grooves and cause lots of trouble.

Special pliers should be used for spreading the rings, as they must work in exactly the opposite manner from ordinary pliers; that is, the nose should open instead of shut when the handles are brought together. Such pliers may be purchased ready-made, but are easily constructed from pieces of steel rod bound together with wire for a joint as shown in Fig. 150. Oftentimes rings will fail to hold compression when they are not

worn out, through oil becoming gummed and hardened in the groove, thus preventing the rings from moving about or springing properly. If the grooves are found filled with hard oil they should be thoroughly cleaned and freshly oiled before replacing either old or new rings. If the rings show smooth and bright all around it proves that there is no leakage past them, but if blue-black or discolored spots show it indicates a leak. In cylinders

Fig. 150.-Pliers for Spreading Rings

with separate heads, where the piston is lifted up through the top, it is often very difficult to replace the piston and rings. By placing bolts or screws in the stud holes of the cylinder and pushing wooden wedges between these and the rings, the piston may be easily replaced (Fig. 151, W). Strips of brass or tin may also be used as shown in Fig. 152, S, S, and will save trouble and broken rings.

Most engines have considerable bright brass work about them, and it adds greatly to the appearance of any motor to have this kept bright and clean. Hundreds of metal-polishes are on the market and some of these are good, some poor, and some will destroy the metal faster than they polish it. Avoid any polish that cleanses by Any polish that smells of ammonia or that will affect litmus paper for an acid test should be avoided by all means. Such polishes will give a

chemicals or acids.