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Section 4 Engine Service
Service Information
Before starting any maintenance, trouble-
shooting, or service procedures, the appropriate
service information should be consulted. Basic
maintenance and service information can often be
found in the owner’s manual provided with the
implement or the engine itself. The owner’s man-
ual typically includes information on maintenance
schedules, fl uid capacities, and part numbers for
maintenance components (fi lters, spark plugs,
etc.). It may also include very basic maintenance
and troubleshooting procedures. For example,
the owner’s manual may include instructions for
changing an engine air fi lter or diagnosing a no-
start condition.
Many engine and implement manufacturers make
copies of their owner’s manual available online. These
manuals can often be accessed free of charge.
A service manual contains more detailed infor-
mation than the owner’s manual. Service manuals
are often published for each engine type a manu-
facturer produces. For example, one manufacturer
publishes a manual for all variations of the single-
cylinder engines it produces, and another manual
for all two-cylinder engines it makes. Some com-
panies publish service manuals for engines from a
variety of manufacturers.
Service manuals can generally be purchased
directly from engine manufacturers, as well as
from aftermarket publishers. Often, you can pur-
chase service manuals at shops that sell engines
and engine parts.
Service manuals generally include comprehen-
sive service procedures, detailed drawings of vari-
ous engine assemblies, and troubleshooting charts,
Note
Many M Ma y en n ng ine n an d d impleme en t manufacturers make
copie co o e es o o o f their h owner’s w manual n available online. These
manuals m ma u s s ca an often e be acce es sed free of charge .
as well as a variety of tolerances, clearances, and
specifi cations needed to properly troubleshoot and
service a specifi c engine.
The service procedures found in most manuals
list the steps to take in order to accomplish a task
effectively. The detailed drawings of assemblies and
systems are often exploded views that can help you
disassemble and reassemble parts in the right order.
Troubleshooting charts list the most common
engine troubles along with possible causes and
suggested remedies. See Figure 13-31.
Engine specifi cations, tolerances, and clear-
ances are also given in a service manual. See
Figure 13-32. When tolerance specifi cations show
two values, the actual dimension must be some-
where between the two values. In Figure 13-32, for
example, the cylinder bore (diameter) must mea-
sure somewhere between 2.1260″ and 2.1265″.
Engine Identifi cation
In addition to having the correct service infor-
mation, it is important to identify the exact model
engine you are servicing. This will allow you to
locate the proper specifi cations for the engine. It
will also help ensure that you order the correct
repair parts.
Most engines have a model number displayed
on a sticker affi xed to the engine housing or to the
engine itself. On some engines, the model number
is stamped into the engine block, the metal shroud,
or some other engine component. The model num-
ber will provide you with specifi c information
about the engine at hand. For example, it will gen-
erally provide you with information on crankshaft
orientation (vertical or horizontal), starter type
(recoil start or electric start), carburetor type, etc.
In addition to the model number, some manu-
facturers use ID numbers, serial numbers, or other
code numbers that convey additional information.
See Figure 13-33. These numbers may identify
unique features of the engine. For example, the
engine used on a certain model of lawnmower may
have a crankshaft with a special snout to accom-
modate the mower’s blade. The numbers may also
provide information on the date of engine manu-
facture, the location of the assembly plant, the
engine warranty, emissions control compliance,
etc. Information on interpreting model numbers,
as well as other engine identifi cation numbers, can
be found in an appropriate service manual.
Air Escaping from: Indication:
carburetor intake defective intake valve
exhaust system defective exhaust valve
crankcase breather defective piston rings
Figure 13-30.
The chart shows the location of air leaks and the
indicated defects.