Leaks may be detected in the connections by spurting a little water on the joints, and turning the engine over on the suction stroke. If the water is sucked in the leaks should be repaired at once. Make sure when placing gaskets, that the gasket does not obstruct the opening in the pipe, and that it is securely fastened so that it is not drawn in by the suction.
Never allow the carburetor to support any weight, as the shell is easily sprung which will result in leaking needle valves.
=CARBURETOR ADJUSTMENT.= When adjusting the carburetor of multiple cylinder engine, it is advisable to open the muffler cutout in order that the character of the exhaust may be seen or heard. With the muffler open, the color of the exhaust should be noted. With a =PURPLE= flame you may be sure that the adjustment is nearly correct for that load and speed; a yellow flame indicates too much air; a thin blue flame too much gasoline, and is not the best for power.
Before starting for the adjustment test, try the compression, and the spark. If the compression is poor, try the effects of a little oil on the piston, which may be introduced into the cylinder through the priming cup. It will be well to dilute the oil to about one-half with kerosene. After all trouble with all the parts are clear, you may start the engine.
Turn on the gasoline at the tank, and after standing a moment see whether there is any dripping at the carburetor, if there is, the trouble will probably be due to a leaky float, dirt in the float valve, or to poor float adjustment. Locate the leak and remedy it before proceeding further. Dirt on the seat of the needle valve may sometimes be removed by “flooding” the carburetor, which is done by holding down the “tickler” lever for a few seconds, causing the gasoline to overflow, and wash out the dirt.
If the motor has been standing for a time it would be well to “prime” the motor by admitting a little gasoline into the cylinder through the priming cup, or by pushing the tickler a couple of times so as to slightly flood the carburetor.
Now turn on the spark and turn over the engine for the start, taking care that the throttle is just a little farther open than its fully closed position. If the engine takes a few explosions and stops, you will find the nozzle, or that some part of the fuel piping is clogged which will stop the engine. If the motor gradually slows down, and stops, with =BLACK SMOKE= issuing from the end of the exhaust pipe, or =MISFIRES= badly, the mixture is =TOO RICH=, and should be reduced by cutting down the gasoline supply by means of the needle valve adjusting screw. If it stops quickly, with a =BACKFIRE=, or explosion at the supply of gasoline should be =INCREASED= by adjusting the mouth of the carburetor, the mixture is =TOO LEAN=, and the needle valve.