Engine smokes. Black smoke; mixture too rich. Blue smoke; too much oil. Broken or stuck piston rings. Poor oil. Engine backfires Mixture too lean. through carburetor. Sticking inlet valve or weak inlet valve spring. Explosions in exhaust Missing spark. pipe. Mixture too rich. Sticking exhaust valve. INDEX Adjusting a carburetor, 213 Advance of ignition; theory of, 18 Air cleaner or washer, 71 Air inlet; extra, 63 Armature, 106 Atwater-Kent ignition system, 136 Automatic carburetor, 63 Automobiles and tractors compared, 1 Axles; types of front, 172 Backfire, 55 Balance weights, 31 Bearings, 31 Bosch magneto; theory of, 110 Bosch magneto circuit, 111 Bosch magneto windings, 110 Bull gear drive, 165 Burning point of oil, 182 Cam, 39 Carbon; formation of, 56 Carbonization, 56 Carbon; removing, 242 Carburetor, 57 Carburetor action, 60 Carburetor adjustment, 213 Carburetor adjustment for two fuels, 218 Carburetor; compensating, 63 Carburetor connections, 89 Carburetor; description of, 72 Carburetor; float feed, 76 Carburetor; heating the, 70 Carburetor; parts of, 70 Carburetor; pump feed, 80 Carburetor; stopping on gasoline, 218 Carburetor strainer, 89 Carburetor; trouble with, 215 Carburetor; using water in, 219 Causes of trouble, 259 Centrifugal force, 94 Change speed gear; action of, 152 Change speed gear; jaw clutch, 156 Change speed gear; purpose of, 6 Change speed gear; shifting, 203 Change speed gear; sliding, 154 Change speed gear; theory of, 149 Choke, 67 Circuit; Bosch magneto, 111 Circuit breaker; magneto, 110 Cleaner; air, 91 Clutch; action of, 144 Clutch; expanding, 145 Clutch; how to use, 205 Clutch; plate or disk, 146 Clutch; purpose of, 6 Cold weather care of tractor, 207 Cold weather starting, 207 Combustion space, 11 Combustion; theory of, 52 Compression; importance of, 16 Compression leaks; locating, 228 Compression stroke, 16 Compression; testing the, 227 Connecting rod, 35 Cooling system, 46 Crank shaft, 30 Cycle; gas engine, 11 Dead strokes, 12 Differential; action of, 161 Differential; purpose of, 7 Differential; theory of, 158 Dirt in the fuel, 215 Disk clutch, 146 Distributor; magneto, 124 Dixie magneto action, 119 Double bowl carburetor; adjustment of, 218 Double opposed engine, 25 Drive; master gear or bull gear, 165 Drive; purpose of, 6 Drive; worm, 166