Engine
Disassembly
DISASSEMBLY/ASSEMBLY
When complete engine disassembly is necessary,
first removeall complete assemblies. Individual assem-
1.
Use the proper bearing driverto install front main
bearing after coating
it
with a light film of oil.
2.
Insert rear main bearing in rear bearing plate.
3. Insert crankshaft,rear bearing plate, and crank-
blies such as fuel pump and carburetor can be
disassembled and repaired at another time.
shaft gear.
Suggested Disassembly Order
1.
Drain crankcase.
2.
Disconnect all exhaust lines and electrical lines.
3.
Remove engine from its mountings and place on
4.
Remove all housings, shrouds, blower housings,
5,
Remove flywheel, using a puller.
6.
Remove the gear cover, being careful to protect
the oil seal from keyway damage.
7.
Remove the crank gear, using a gear puller and
ring.
8.
Remove all accessories such as oil filter, starter,
intake manifold, fuel lines, spark plugs, etc.
9.
Remove breaker point box.
10.
Remove oil base, oil pump and cylinder heads.
11.
Remove valves, springs, lifters, etc.
12.
Remove camshaft and gear assembly.
13.
Remove connecting rods and pistons.
14.
Remove rear bearing plate, crankshaft, and front
a suitable bench or work stand.
etc.
bearing.
4.
Install piston and connecting rods.
5.
Install camshaft and gear assembly; align crank
gear mark with cam gear mark.
6.
Install valve assemblies, oil pump, oil base, and
cylinder heads.
7.
Install breaker point box.
8.
Install all accessories such as oil filter, starter,
9.
Install gear cover with oil seal and flywheel.
10.
Set breaker points to obtain proper timing.
11.
Check valve clearance.
12.
Install all housings and air cleaner.
13. Fill crankcase with oil.
fuel lines and spark plugs.
Operation
Start engine and check oil pressure. Run for approx-
imately 15 minutes to bring engine to operating
temperature. Check for oil leaks, fuel leaks and
exhaust leaks. Adjust carburetor and governor for
speed and sensitivity.
Testing Compression
The compression tester
is
used
to
determine
the
condition of valves, pistons, piston rings and
cylinders.
Keep all parts in their respective orders. Keep valve
assemblies together. Return rod caps to their respec-
tive pistons. Analyze the reasons for parts failure.
Suggested Assembly Procedure
Engine assembly is normally the reverse
of
the
disassembly procedure, observing proper clearances
and torques. Use a torque wrench to assure proper
tightness. Coat the internal engine parts with oil
as
they are assembled. After the internal engine parts
are assembled, the engine should turn over by hand
freely. Use onlygenuine Onan partsand special tools
when reassembling your engine.
To check compression:
1.
Run the engine until thoroughly warm.
2.
Stop engine and remove spark plugs.
3. Remove air cleaner and place throttle and choke
4.
Insert the compression gauge in one spark plug
5.
Crank the engine and note the reading.
in the wide open position.
hole.
Refer to
SPEClFlCA
TlONS
section for compression
pressures. There may
be
variations due to temperature,
atmospheric conditions and altitude. These pressures
are for a warm engine at cranking speed (about
300
rpm).
10-1
Redistribution or publication of this document,
by any means, is strictly prohibited.
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