245
Chapter 13 Preventive Maintenance and Troubleshooting
The small engine manufacturer will recommend
oil changes at intervals based on hours of running
time. A new engine should have the fi rst oil drained
after only a few hours of operation to remove any
metallic particles from the crankcase. After that, the
time specifi ed may vary from 10–50 hours.
Engine oil does not wear out. It always remains
slippery. However, oil used for many hours of engine
operation becomes contaminated with dirt particles,
soot, sludge, varnish-forming materials, metal par-
ticles, water, corrosive acids, and gasoline. These con-
taminants eventually render the oil useless. The harm
they cause outweighs the lubricating quality of the oil.
The time interval for oil changes is selected so
that the oil never reaches a loaded level of contami-
nation. Loaded oil cannot absorb any more con-
taminants and still be an effective lubricant. When
oil reaches a loaded condition, varnish deposits
begin to form on the piston and rings, and sludge
collects in the crankcase.
Changing Oil
Changing engine oil is not diffi cult. Begin by
running the engine until it is thoroughly warmed
up. Warm oil will drain more completely, and more
contaminants will be removed if the oil is agitated.
Turn off the engine and disconnect the spark
plug. The oil drain plug is located at a low point
on the crankcase, usually along the outside edge of
the base. See Figure 13-4.
Some engines do not have an oil drain plug. Oil must
be drained through the fi ller hole on these engines..inesgen
Clean the dirt from the drain plug area and
then remove the plug with a proper wrench,
Figure 13-5. Allow the oil to drain for approxi-
mately fi ve minutes to remove as much contami-
nated oil as possible. See Figure 13-6. If the drain
hole is located on the side or top of the engine, tilt
the engine toward the drain hole if possible. When
draining is complete, replace the drain plug.
Note
Some S o me engines n d o o no t have e an oil drain plug. Oil must
be be e drained r n n through g the fi ll e e r ho le on these
S S o o m me e e ng in n e s d o o no t ha e e an oil drain pl g Oil m st
Figure 13-4.
The oil drain plug is located at a low point in the
crankcase to permit oil to drain completely.
Drain plug
Figure 13-5.
This technician is using a socket and ratchet to
remove the drain plug. The plug should be turned
counterclockwise for removal.
Socket
Figure 13-6.
It may take several minutes for all the old oil to drain
from the engine.
Drain plug