after the following several details you will not only ,et the full rated horsepower out of your engine, but you will get it with the least amount of fuel, the repairs and shutdowns will be few and far between, the interest on the money you have invested in it and the depreciation of it will both be small, and, finally, the life of the engine will be long.

Named, these details are that you must (1) burn the right kind of fuel and see to it that (2) the fuel valve or carburetor is adjusted correctly; (3) the lubricating oil is the best and exactly suited to your engine; (4) the drain cocks are all closed; (5) there is no soot in the exhaust pot or muffler; (7) the gaps of the spark plugs are of the right length; (8) the ignition system is timed correctly; (9) likewise the valves are timed correctly; (10) there is no carbon in the cylinder; (11) the bearings all around fit precisely, and, lastly, (12) that you make a study of your engine, and know exactly how every part of it works.

CHAPTER IX

DISEASES OF INTERNAL COMBUSTION ENGINES

An internal combustion engine of whatever kind or make is very like a human being, in that if it isn't looked after and treated well it will be sure to develop some disease, and so go into an early decline; and sometimes, too, exactly like the mechanism of a man, it will ail and growl around when there isn't a thing on earth the matter with it.

In the foregoing chapter I mentioned that there are three general symptoms by which you can tell when something has gone wrong with your engine, but what I did not tell you was that each symptom may indicate any one of a dozen different troubles, and to find the offending one you must know the specific symptoms of it.

Now, while it might seem on the face of it to be a pretty hard matter to locate the fault, since there are so many of them-fixing it is easy when you know what to fix-it is not at all a hard job if you go about it the right way, and this is by the process of elimination.

When the Engine Works Badly.-The Seat of the Trouble.-When the engine works poorly it may

be caused by (1) a priming cock that leaks; (2) poor compression caused by a loose or a broken sparkplug; (3) or trouble with the ignition system; (4) gaskets that leak; (5) the use of lubricating oil that has too light a body; (6) piston rings that give too much clearance; (7) piston rings that are bent or are otherwise faulty; (8) a broken lockpin in the piston ring, or (9) valves that do not seat properly.

Finding and Fixing the Fault.-The order I have given above is the one in which you should look for the fault and after testing each one out thoroughly see if the engine works all right or not.

Begin, then, by looking after (1) the priming cocks; if the leak is bad the sound of escaping gases around the loose one will indicate it clearly enough; if there is no sound, squirt a little oil on it where it screws into the cylinder head, and if it leaks little bubbles will rise in the oil.

To fix it try tightening the cock up with a wrench and if you can't get it tight enough to keep it from leaking put a little red-lead on the threads and then screw it up. (2) Sometimes a spark-plug gets a little loose or the threads are worn. To find out whether it leaks squirt a little oil around the threads and watch for the bubbles as explained above. Tighten it up and use some red-lead on the threads if necessary. If the spark-plug is cracked there will be a considerable loss of compression through it, and when this happens you can hear it wheeze, and to fix it all you have to do is to put in a new plug.

(3) When there is no leakage from the spark-plugs or gaskets and the compression seems to be good, examine the ignition system very carefully and look particularly for a loose wire or a grounded wire, by which I mean a wire that has worked loose in its binding post or one whose insulation has been rubbed off and so makes a slight contact with some other wire or with the engine itself. When you have attended to these details the chances are that your engine will run as well as it did when you bought it, provided you bought a new one.

(4) If the gaskets leak you will know it by the wheezing sounds of the exhaust gases. It may be that the nuts are loose and tightening them will do the business, but do this while the engine is hot.

Should the gaskets be worn out or rotted out, cut new ones out of asbestos packing1 which has a brass or bronze wire mesh in it. When you put on a new gasket smear both sides of it with linseed or lubricating oil and tighten the bolts up when the engine is hot. (5) The next thing to try is a lubricating oil having a heavier body than the one you are using; to do this unscrew the drain plug from the crankcase and run out all of the old oil. This done, screw in the plug and fill the crankcase, or sump, below it, whichever it is, to the oil level with kerosene.

Now run the engine slowly for half a minute or 'The Johns-Manville Co., 41st St. and Madison Ave., New York City, sell it.

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so, when it will clean out the working parts of the engine. Take out the drain plug again and run out all of the kerosene, put back the drain plug and fill the crankcase or sump with the heavier grade of lubricating oil. If nothing else is the matter you will find that your engine will develop more power than you ever gave it credit for.

After you have attended to all the above easy things, if the compression is still poor, it is then time to conclude that (6, 7 and 8) the piston rings are at fault, or else (9) the valves do not seat as they should.

(6, 7 and 8) To clean, or replace faulty piston rings with a new set, take off the oil shield or crankcase and remove the nuts from the bolts that hold the crank bearings in place. Turn the crank to its outer dead center and you can then pull the piston out of the cylinder. The next thing to do is to clean it with a solution of hot lye and water, then wipe it dry and wash it off with kerosene.

To take off the piston rings raise up one end of one of the rings, slip a strip of tin, about 11⁄2-inch wide and 5 or 6 inches long, under it and work it around until it is midway between the ends of the ring. This done, slip another strip of tin under each one, as shown at A in Fig. 69, when you can easily push the ring from the groove it seats in and off of the piston.

Iron piston rings can be expanded and then slipped over the head of the piston onto their grooves