PISTON AND RINGS.

As explained on page 6 what makes the engine run is the combination of air and gas drawn into the cylinder by the suction of the piston, this gas being compressed before it is exploded. To compress this gas it is necessary that the space in the cylinder be gastight. The piston is fitted to the cylinder and makes a fairly tight joint, but on account of the expansion of iron when it gets hot, it is necessary to have some o t h e r means of keeping the gas from escaping. Each piston is fitted with three rings that spring out and press against the walls of the cylinder, making a gastight chamber.

These cylinder rings hold the compression and must fit free in the grooves of the piston. Feeding a poor grade of gasoline or lubricating oil, or too much of either, will cause a carbon deposit to form around the rings, which will in time bind them in the grooves, so they cannot spring out against the walls of the cylinder to hold the compression. It is very necessary that you use the proper grade of oil and watch the supply of gasoline, as on this depends the proper running of the engine.

To remove the piston from the cylinder, take out the connecting rod bolts at the crank shaft end of the connecting rod. Remove the bearing which loosens the connecting rod from the crank shaft. Next, you will have to take off part of the governor, remove the governor pinion, as instructed on page 10, which gets the spindle and balls out of the way. This is all of the governor that you will have to take off, as the piston will now slip out of the cylinder.

If you find the piston rings are gummed or held tight in the grooves, they must be cleaned thoroughly. To do this you will have to remove the rings and wash them in kerosene or gasoline and you may have to scrape them with a knife.

To remove the rings take three thin metal strips and slip tinder the center ring. Start the first strip under the ring at the joint and force it all the way around until you have it at the position shown by "A," Figure 10, then slip the second strip to "B" and the third to "C," which will raise the ring out of the groove so it can be slipped off. Take the top ring next and repeat the operation; then the bottom ring.

In replacing the rings, put the center ring in first, using the three metal strips as before, then without the three metal strips you can slip the top ring on and then put the bottom ring on, bringing it up from the bottom of the piston. Before putting the piston back in the cylinder, oil the rings and surface of the piston thoroughly.

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