FARM OIL ENGINES.

Hauraki Plains Gazette, Volume XXXIII, Issue 4384, 1 March 1922, Page 4

FARM OIL ENGINES.

(Continued from page 3.) old piston, arid have a new liner to fit. In the case of defective circulation remive the connection between tihe Cylinder jacket and the - tank, and clear the pipes. Also flush the accumulated sludge out of the water jack l -, et. Failure to Start. —Tjiis may be due to* (1) Tube not hot enough. (i2) Flooding. (3) Faulty spark plug. (4) Magneto points pitted or tpo far apart. (5) Incorrect mixture. (6) Loss ?f magnetism. The remedy for No. 1 is obvious. No. 2. This, in the ‘case of tube ignition, is due to No. 1. * The tube not being hot enough, fails to' ignite the changes drawn in, and; lying in the cylinder in a liquid state, they make firing difficult, if not Impossible. Shut off the supply from tank and thru engine by hand till the cylinder is clear, then try again. V In the case .of an engine fired by a spark plug, flooding ma’y be due to too much benzine. This can be seen if the plug is soaked. Shut off the supply. open the compression- cock, and turn the engine bill an explosion occurs. Then shut’ the ’ compression cock, turn on the benzine about threequarters of a turn, and crank the engine. It ought to start. If not, and flooding still persists, examine the float in the carburettor. It will probably be punctured, ( No. 3. The plug may be sooted-up, due to using too rich a mixture, or it may be dirty from too much lubricate ing oil, or the spark gap may-be set too wide, oi* moisture may,have bridged the points duririg.a'cpld night. If soot is present, reduce the benzine or kerosene, or increase the air. In the case *of a' splash lubricated engine, see that the rod dips only , half an inch into the oil in the* crank chamber.'* If a sight glass feed is installed, see that only five drops per minute are being measured out to the piston. The points of the spark gap should be only about ,l-32in apart. As an engine cools down after a run a certain amount of air finds its way into the cylinder, and if the night is very cold this will condense and collect between the points of the plug, mailing starting impossible till got rid of. No 4. If the magneto points are pitted, iti will be necessary to procure a magneto file, specially made for the purpose, and place it'“between the points, carefully working ■it backwards and forwards till a clean, level surface is obtained. After doing this the point's should be adjusted till they are l>.64in apart. If they are wider a spark will occur between them, and not at the spark plug . No. 5 may be due to too much benzine, or too much air, or. both. The remedy is to treat as instructed for flooding. Shut off the tank supply and turn the engine till sure all the mixture is out of qyliridei- . Then turn on the needle valve of the carburettor about three-quarters of a turn, shut off ,the air, and start, the engine. When running, open the air throttle. Nov/, if the engine blows hack in the carburettor, and “pops,” it is a sign of weak mixture. Gradually turnon the benzine till this symptom ceases. No. 6. This is due to the magneto being dropped' or having been subjected to a heavy jar, and it may be due to the armature having beep removed and no piece, of iron or steel being placed on the pole pieces while the armature is undergoing repair. It may be detected by holding the spark plug cable in the hand while the engine is being turned over. If no shock is felt the magneto should be forwarded to a firm of electrical enn gineers for re-magnetisation. Knocks in Engines.—The causes of knocks are many and various, but a little practice soon enables the operator to discover the seat of the trouble. Only a few can be dealt with here, but they will probably embrace, all likely to be met with in the running of a small engine.

No. 1 : Too Rich a Mixture.—This causes a dull, heavy pound in the cylinder, with the engine running irregularly and becoming overheated. Dense black smoke comes out of exhaust pipe. The remedy is to cut down the benzine or increase the air supply. No. 2: Tube Too Hot.—The engine knocks heavily on explosion stroke only. The mixture is being fired too soon, and meets the piston on the up stroke. Remove the cover from the ignition tube, and allow the atmosphere to cool it down. Practice -.will soon show the correct temperature at which it works most satisfactorily.

No. 3: Pre-ignition or Automatic Ignition.—This occurs when carbon is present in the cylinder, and becomi ing redhot fires the charge before the electric spark is due. This pre-igni.-tion . almost invariably fires ’ the

charge before the compression stroke is two-thirds\.comp'leted, and the force of the explosion hits the piston so violently that it may even reverse its direction of travel and stop the engine very abruptly. In some cases the engine will, continue to run, but with great knocks and jerkings. The cylinder should be taken down and all carbon deposits removed by means of a scraper. No. 4': Spark Too Far Advanced. — The same symptoms appear as for ■pro-ignition, and these are due to the spark occurring on the up-stroke of the piston. It is just as well to men-, tion here that an engine running on a heavy' load will not take the same amount of spark advance as one running light or with a load well within its capacity, Retard the spark by bringing the lever down in the direction of the magneto’s rotation —and the trouble will cease.

No 5 : Loose Crosshead Bearings.--This is noticeable by a sharp rattling sound, and cannot be mistaken for any other, engine knock. Take off the crank bearing brasses and draw out the rod with’ piston attached. Remove the crosshead pin and /refit ths bearing by means of the adjustment provided by the makers. Do not be afraid to set the bearing, up fairly t'igljt, as it will ease off with the heat when running. The correct adjust ment is that which will; just allow the rod to fall slowly .of its own weight when the crosshead pin is held in a vise. No. 6: Loose FlywheeV-rr-Tjiis is known by a sharp jerking noise, and occurs when the engine is bn the com.--pression stroke. It is capable of the most destructive effects, ,and must be attended to at once.. If neglected it will ' probably necessitate the purchase of a new engine. The remedy, of course, is to see that the key is driven tight into the wheel, and, if necessary,- have a new key fitted by an expert mechanic. Irregular Running?—l will mention two eases which came under my notice. as. it is possible many of you may have experienced something of a similar nature without having been able to find ,the cause. The first was that bf an engine which started up easily, ran for about ten minutes, and then stopped.' An examination of carburettor showed plenty .of benzine, The spark plug, on being taken out, showed correct separation of the points and perfectly clean. It also showed a good spark when laid on top of the engine. Apparently everything was. correct! The plug was replaced and the engine tried again, and as before started at once and run for ten minutes, then stopped dead. The stoppage, was sc abrupt that I knew it to be the ignition, and concluded the truble was in the plug, in spite of the fact that it.testled well and showed good spark. The plug was' changed and the engine ran splendidly. That the diagnosis was correct was borne out by an examination of the porcelain of the plug with a powerful magnifying glass, which distinctly showed a very fine crack. As the engine heated the plug, this crack opened and allowed the current to pass to earth without firing the charge. The second case was one in which the engine started up easily and ran for the same length pf time. With the previous experience before me, I changed the plug, but to my surprise it was of no avail, the engine stopping as before. I found the; tank Tian plenty of fuel, and the pipe to the carburettor was clear and everything apparently all right. I started the engine again, and. it! ran as before, and for the same leji£*• ■> of time, and then stopped. I 'Pad been doing a bit of hard thinking during this run, and immediately the engine stopped I shut/off the suou'y from the tank, removed the cover of the carburettor, and, as I suspected, found it empty. The source of the was evidently in the connection between the tank and the carburettor, and in spite of the fact tat I knew the pipe to be clear T decided it was the pipe, and an examination of it proved I had hit upon the troubleThe pipe was a fairly long one, and had been bent and twisted to make it fit into position. One part of it was higher than the supply cock from the tank, and in this elevated part air .had collected and (formed an air lock. This prevented fuel in sufficient quantity passing'to the engine, and the gradually diminishing supply brought the engine to a standstill. When the engine stepped the carburettor gradually filled up again, and enabled a fresh start to be made. I straightened the pipe, giving it a gradual fall to the carburettor, and it given no further trouble.

Loss- of Compression.—Horizontalj engine. A peculiar case of this de- ' scription came under my n'otice. The engine started up easily and ran well for a time, then started to pass the charge'past the rings outlbAthe front

of the cylinder. It also showed signs of having too rich a mixture by becoming very much overheated. I could not understand tjiis last feature, as an examination of\ the discharge from the exhaust! pipe showed no visible sign of anything bu - a perfect mixture, while the engine was running. 1 would like to give you a Simple guide whereby you can tell if your mixture is correct by an ext amination of the discharge from the. engine exhaust. If an examination shows black smpke you are using too, much benzine or, kerosene. If white smoke, too much lubricating oil in the cylinder, and, if the discharge is not visible, you can rest assured you are using a perfect mixture. Well, to get back to fhe point where I said I could not understand the engine: overheating, as I knew the mixture to be correct. Knowing also that the engine had good compression when ■cold, I concluded the ifault lay in the water-cooling system, and tlhat the water 'was not circulating in the Cylinder jacket. This supposition proved correct, tor on removing the connection to the water jacket from tihe tank I found the “expert” (?) who installed the plant had not thought it necessary to leave a passage in the joining material. This fully accounted for the loss of compression. And now, gentlemen, in conclusion, just a word of. advice. Don’t alter any adjustments on your engine without being sure first of what result you. from your,. ignition to your carburettor, but follow one line only at a time, and by so doing you will locate your trouble in the least possible time and along lines which will; be of infinite benefit in the successful running of your power plant.