All exterior parts should be protected by a coat of thick oil or by paint. The governor rod, push rods, and similar parts should be especially looked after. It is advisable to take off the magneto and store it in a safe, dry place; spark plugs should be left in position.
The tractor should be covered with a tarpaulin and stored in a tight shed.
When going over a tractor preparatory to laying it up, a list should be made of all parts that need renewal. These parts should be procured at once; they are more readily obtained during the winter than in the operating season, and will be on hand for the spring overhaul.
CHAPTER XII
ENGINE MAINTENANCE
FUEL SYSTEM AND CARBURETOR
The operation of a carburetor depends on so many things that no exact instructions for its adjustment can be given. The best that can be done is to give a general idea of the requirements, and to outline a plan by which the adjustment can be arrived at.
The many makes and designs of carburetors and vaporizers that are used on tractors have different kinds of adjustments; on most of them the only adjustment is the needle valve that controls the fuel, but some also have adjustable air valves. In any case, the manufacturer’s instruction book should be studied for the understanding of the particular carburetor in question.
The first step in adjusting a carburetor is to get the engine running. The needle valve should be closed, and then opened enough to give a mixture on which the engine will start; on many carburetors this will be about one and one half turns. The engine should then be primed; that is, a little gasoline should be put in the cylinder, which may be done with a squirt can.
When the engine is running, and is well heated, the needle valve should be gradually closed until the engine begins to miss, and to send jets of flame out of the carburetor, or little explosions occur in the carburetor. These are signs of a thin mixture, and the needle valve should be gradually opened to make the mixture richer. The engine will run more steadily, and will pick up speed until the mixture becomes too rich, when it will choke and black smoke will come out of the exhaust.
The positions of the needle valve for a mixture that is too thin and one that is too rich have thus been found, and it remains to set it at that point between at which the engine runs most steadily and at the best speed.