to inspect the machine.

The water-tank was leaking through a crack in the side, but not so
badly that we could not go on to Cleveland, where repairs could be
made more quickly. A slight pounding which had developed was
finally located in the pinion of a small gear-wheel that operated
the exhaust-valve.

It is sometimes by no means easy to locate a pounding in a
gasoline motor, and yet it must be found and stopped. An expert
from the factory once worked four days trying to locate a very
loud and annoying pounding. He, of course, looked immediately at
the crank- and wrist-pins, taking up what little wear was
perceptible, but the pounding remained; then eccentric strap,
pump, and every bearing about the motor were gone over one by one,
without success; the main shaft was lifted out, fly-wheel drawn
off, a new key made; the wheel drawn on again tight, all with no
effect upon the hard knock which came at each explosion. At last
the guess was made that possibly the piston was a trifle small for
the cylinder; a new and slightly larger piston was put in and the
noise ceased. It so happened that the expert had heard of one
other such case, therefore he made the experiment of trying a
fractionally larger piston as a last resort; imagine the
predicament of the amateur, or the mechanic who had never heard of
such a trouble.

There is, of course, a dull thud at each explosion; this is the
natural "kick" of the engine, and is very perceptible on large
single-cylinder motors; but this dull thud is very different from
the hammer-like knock resulting from lost motion between the