9.1
Section 9
Inspection and Reconditioning
9
Section 9
Inspection and Reconditioning
This section covers the operation, inspection, and
repair/reconditioning of major internal engine
components. The following components are not
covered in this section. They are covered in sections of
their own:
Section 4: Air Cleaner and Intake System
Section 5: Carburetor & External Governor
Section 7: Ignition, Charging & Electric Starter
Clean all parts thoroughly. Only clean parts can be
accurately inspected and gauged for wear or damage.
There are many commercially available cleaners
that will quickly remove grease, oil, and grime from
engine parts. When such a cleaner is used, follow the
manufacturer’s instructions and safety precautions
carefully. Make sure all traces of the cleaner are
removed before the engine is reassembled and placed
into operation. Even small amounts of these cleaners
can quickly break down the lubricating properties of
engine oil.
Use an aerosol gasket remover, paint stripper, or
lacquer thinner to remove any old sealant. Apply the
solvent, allow time for it to work, and then brush the
surface with a brass wire brush. Aer the old sealant
is removed, clean the surface with isopropyl alcohol,
lacquer thinner, or aerosol electrical contact cleaner.
Do not scrape the surfaces, as any scratches, nicks, or
burrs can result in leaks.
Refer to A Guide to Engine Rebuilding (TP-2150-A)
for additional information. Measurement Guide
(TP-2159-B) and Engine Inspection Data Record
(TP-2435) are also available; use these to record
inspection results.
Automatic Compression Release (ACR)
Some engines may be equipped with the optional
Automatic Compression Release (ACR) mechanism.
The ACR lowers compression at cranking speeds to
make starting easier.
Camshaft
Inspection and Service
Check the lobes of the camsha for wear or damage.
See Section 1, Specifications and Tolerances for
minimum li specifications. Inspect the cam gear for
badly worn, chipped or missing teeth. Replacement
of the camsha will be necessary if any of these
conditions exist.
Crankshaft
Inspection and Service
Inspect the gear teeth of the cranksha. If the teeth
are badly worn, chipped, or some are missing,
replacement of the cranksha will be necessary.
Inspect the cranksha bearing surfaces for scoring,
grooving, etc. Measure the running clearance between
the cranksha journals and their respective bearing
bores. Use an inside micrometer or telescoping gauge
to measure the inside diameter of both bearing bores
in the vertical and horizontal planes. Use an outside
micrometer to measure the outside diameter of the
cranksha main bearing journals. Subtract the journal
diameters from their respective bore diameters to get
the running clearances. Check the results against the
values in Section 1, Specifications and Tolerances.
If the running clearances are within specification,
and there is no evidence of scoring, grooving, etc.,
no further reconditioning is necessary. If the bearing
surfaces are worn or damaged, the crankcase and/or
oil pan will need to be replaced.
Inspect the cranksha keyways. If worn or chipped,
replacement of the cranksha will be necessary.
To Next Page
Loading...
