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C H A P T E R 1 9
Engine Reassembly and
Break-In
Learning Objectives Key Terms
After studying this chapter, you will be able to:
Summarize the steps in reassembling L-head
and overhead valve engines.
Explain how crankshafts and camshafts
should be reinstalled.
Summarize the steps in reassembling a piston
and rod assembly and installing rings.
Explain the purpose of ring end gap.
Describe methods of adjusting crankshaft
endplay.
Summarize what happens during piston ring
wear-in.
assembly lube
bearing crush
bearing spread
break-in
dampening coils
Introduction
After the engine has been disassembled and all
the parts have been cleaned, inspected, and recon-
ditioned as needed, the engine must be properly
reassembled. Always reassemble the engine in a
clean work area. If dirt or other abrasives get into
the engine during reassembly, it can undo all of the
hard work that went into the engine rebuild.
Have all of the necessary repair parts, supplies,
and instructions handy and well organized. Read
through the manufacturer’s instructions for reas-
sembling the engine and be sure you understand
them before beginning. The instructions provided
in this chapter are general in nature, and may not
apply to the engine you are servicing.
Reinstalling Internal Engine
Components
The steps followed to reassemble an engine are
essentially the reverse of the steps used to disas-
semble it. Begin by making sure that all bearings
or bushings are properly installed in the crankcase
and crankcase cover. Next, install replacement oil
seals in the crankcase and crankcase cover. Apply
sealant around the outside of the shell of the seal
before pressing it in place. Often, seals can be
replaced by tapping them into the bore with a seal
driver. If a seal driver is not available, a socket of
the appropriate size can be used. See Figure 19-1.
If the engine is equipped with a centrifugal gov-
ernor, the governor shaft should be installed next.
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