some time by the forming of little bubbles about joints or gaskets. However, it may come suddenly just after some part has been taken off because the gasket of that part was worn out or it has been fractured in the operation; either will produce the same result, which is, no compression, and consequently no start or a hard one with poor results.

When under way and a leak from the cylinder is suspected, smear the place with oil; if there is a leak, bubbles will force up through the oil.

The side thrust motion to a piston against the walls of cylinders will in time cause a loss of compression; the remedy for this is to have the cylinder reground. This makes the cylinder of greater diameter and may require a different size of ring.

3. Use of Graphite for Poor Compression.-When compression is only moderately poor, but there is difficulty in starting the engine on account of it, a mixture of graphite flux and oil may be squirted into the cylinders. This mixture consists of one part flux to three parts oil. The mixture will settle in the vacant places about the piston and hold the gases; then when the cylinders and piston have become heated the compression will improve of itself. The graphite is a splendid lubricant.

4. Leaky Gaskets.-All the openings into the cylinder are made tight by the use of gaskets or snug-fitting threads. Leaks can be discovered by smearing oil around the joinings. If there is an escape of gas the oil will bubble up. In the case of screwed parts they must be set up tighter or leaded.

The parts protected by gaskets will, when leaking, require new ones. Temporary gaskets may be made of thick brown paper smeared with shellac on both sides; if there is no shellac on board oil will answer in the majority of cases. The shellacked brown paper makes a very efficient gasket and is sometimes used for permanent ones.

Probably the wire-lined asbestos gasket is the most efficient one in use on the average boat. For cylinder heads where many bolts go through the gasket, a punch should be bought

for the size hole required; this saves much labor. For this gasket, place a piece of the material on the cylinder and mark the holes; punch them out and put the piece down over the bolts and with the round end of a hammer rap all around the edges until the gasket is cut out. The asbestos will be cut when hammered over the edge of metal. For irregular gaskets lay the gasket material down on the part and holding it from slipping rap with the round end of the hammer. Good-fitting gaskets can always be made in this way.

When it is certain that all gaskets about the cylinder are in good order and the tanks and carbureter have been cleaned thoroughly, and yet there is water in the cylinder, it is fairly certain that the walls of the cylinder leak. This is a rare occurrence and the best and surest remedy is to return the cylinder to the manufacturer.

5. Miscellaneous Leaks.-If a leak is suspected in the intake pipe between the carbureter and the cylinder, oil placed about the spot will develop the leak by the oil being drawn in if a leak exists. Excessive valve lift will give the same result as a leak. A leaky inlet valve will result in back firing and weak explosions. A leaky exhaust valve will result in weak explosions and in explosions in the exhaust pipes. Vibration can loosen the brazing in the manifold air intake and allow a suction of air, thus giving a weak mixture. Carbon caused by too much oil, also from too much gasoline, will shorten the life of cylinders rapidly.

When a cylinder is out of commission and the engine must be kept running, open the petcocks of that cylinder.

PISTON-RING TROUBLES

6. Removing Carbon.-Piston rings wear slowly and a number of seasons are required to produce any effect on them. Carbon is their greatest enemy. To prevent carbon, the cylinders should be given two or three tablespoonfuls of kerosene each week, or twice a week if the engine is operated to any extent. Some authorities advocate putting the kerosene in

and letting it stay overnight, with the idea that the evaporation of the kerosene overnight will not leave any cause for a poor mixture in the morning. Another method is to put the kerosene into the cylinder and work the engine by hand a number of times for the purpose of washing the inside of the cylinder and working the kerosene down through the rings. More kerosene should then be put in for the flushing effect, or to get rid of what has been dislodged. This should be followed by a number of drops of cylinder oil. Kerosene is a good cleaner, but it will be followed by rust if left to dry by itself. The face of a well-kept cylinder should be as polished as a mirror. The polish is necessary if the cylinder is to give good service. The slow evaporation of kerosene on it will do no good.

FIG. 1

7. Regulation carbon removers are apt to be made of one part aceton and nine parts wood alcohol. They will thoroughly remove carbon, but the polish is apt to go with the carbon. When using the regular carbon remover put it into one cylinder at a time, but leave it in only hour. When that cylinder is cleaned, start the motor and give that cylinder a little extra oil; then clean the rest in turn.

8. Removing Piston and Rings. When it is necessary to take out the piston and clean the rings, the best way is to put the whole piston into a can, or vessel of some kind, containing a quantity of kerosene. Then work the rings back and forth in their grooves, sousing them up and down occasionally to wash the carbon from behind. When the washing is ended it will not take long to dry the kerosene; this is the time the rust starts. Put some oil into the rings and work them a little; a mere skimming of oil is all that is required. Wipe the piston all over with a cloth on which a few drops of oil has been placed. This will prevent rust and put the piston in good shape.

To take off the rings some pieces of clock spring or brass should be provided. Pry one end of the ring up gently, with a piece of very hard wood if it can be secured, until the flat band of the clock spring a can be slipped under it, as shown in Fig. 1. Slide the piece of spring along but before the end of the ring has come down into the groove slip another piece of spring under it, and so on until the ring is resting entirely on pieces of clock spring; then slip the ring off the piston.

When a sudden loss of compression, or a hard resistance to running is manifested, it may be due to carbon having caked and the play of the rings thereby stopped. Under these circumstances, there is danger of the rings being broken.

VALVE TROUBLES

9. The opening of the inlet valve too early will cause back firing. This is due to the ignition of the fresh charge in the inlet pipe and carbureter by the flame remaining in the cylinder from the previous explosion.

The strength of a valve spring may be tried by slipping the end of a long screwdriver or similar tool under one end of it and compressing it. If found weak, compared to the resistance of the others, put in another spring. A spring can be strengthened temporarily by stretching it.

The staying open of a valve when it should close may be due to a weak spring but it is more apt to be from a bent stem or from carbon on the stem. The carbon may be removed from the stem by soaking it in kerosene and tapping it out, having a piece of wood between the hammer and the valve stem.

CRANK-CASE DIFFICULTIES

10. Crank-Case Requirements.-The crank-case must of necessity be air-tight in a two-cycle engine, for in it the fresh charge of mixture is to be compressed to the extent of from 2 to 7 pounds, according to the make of the motor. To be efficient it must also be free from excess oil, and should be entirely free from sediment. Sediment in the crank-case will

be picked up by the lower end of the connecting-rod in its revolutions and carried by the splashing to the sides of the piston, and by the piston to the walls of the cylinder. Smoke issuing from the crank-case indicates that the crank-case is not air-tight and that the piston is leaking exploded gas past its rings from the cylinder.

11. Explosions in the crank-case of a two-cycle engine are due to a lack of fuel in the mixture and are caused in the same manner as back firing in the inlet pipe. All crank-cases should have a drainage cock so that they can be cleaned frequently. Where the chamber is bolted together horizontally through the center, the joint may be made tight by coating both sides of the gasket with graphite. The oil in the crank-case should rise high enough to be inch deep on the lower ends of the brasses on the connecting-rod.

12. Cleaning the Crank-Case.-In many cases, the crank-case of a two-cycle engine will become so filled with oil, gasoline, and dirt, that a proper mixture is impossible. It should first be drained by means of a drainage cock, or a nut, at the bottom, which may be opened or taken off. It should then be flushed out well with gasoline to clean it of dirt and grit. When the cleaning operation is over some oil should be put into the case so that the connecting-rod can splash it up and oil the brasses, otherwise the brasses may be burned out. A handy way to take the excess oil out of the crank-case is by means of long-stemmed squirt guns, or syringes. A clever method of oiling the crank-shaft bearings is with a squirt-gun oil cup. They are rigidly attached to the crank-cases and the oil squirted in with a plunger action.

13. Loss of Base Compression.-In two-cycle motors, there may be loss of compression in the crank-chamber where the shaft enters and leaves the base. The check-valve in the base of two-port, two-cycle motors may not seat well because of dirt, carbon from base explosions, or from a weak spring, thus causing loss of compression. There should be from 2 to 5 pounds compression in the crank-chamber according to the