Onan 6GO-F - Engine

MAINTENANCE AND REPAIR
GENERAL.- Refer to the SERVICE DIAGNOSIS section for assistance in
lo.cating and correcting troubles which may occur. The information
in this section is intended to a.ssist in properly maintaining the
,equipn1ent ami in making repairs. Should a major overhaul become nec-
essary, it is recommended that the plant be carefully checked and all
necessary repairs made by a competent mechanic who is thoroughly fazni1-
iar with modern internal combustion engines and revolving armature type
generators.
ENGINE
TIMING GEARS.- The crankshaft and camshaft timing gears are keyed to
their respective shafts. The camshaft gear is fastened with a large
hexagon nut and locking washer. The gears may be removed with a gear
puller. Always install both gears new when either needs replacing,
never one only. The crankshaft, gear has one tooth punch-marked, which
must mesh
with the two teeth punch-marked on the camshaft gear. See
the illustration. TIMING GEARS, Fig. E.
TAPPET ADJUSTMENT.- The tappet adjustments may be reached by removing
th,e
valve chamber cover. The tappets ar,e the adjustable screw type,
requiring three wrenches to adjust.. See the illustration, TAPPET
ADJU~T, Fig. F.
Adjust the valves for each cylinder as follows. Crank the engine by
hand until the intake valve opens and closes. Both valves for that
cylinder will then be closed. Intake valves are numbers 2, 3,6 and 7.
The adjusting screw clearance should be set to 0.012" for both the
intake and exhaust valves. On engines which have the "Roto" type ex-,
haust valves, set the exhaust valve tappet clearance to 0.010". Make
sure the lock nut on each adjusting aerew is secure~ tightened after
the adjustment is made. Tappets set too close may cause burned or
warped valves, seats, and scored tappets or camshaft lobes. Uake a
final check with the engine running at idle speed.
VALVE SERVICE.- The proper seating of the val.ves is essential to good
engine perfonnance. If anyone valve is leaking, service all valves.
Each valve, its guide, piston top, the cylinder head, anc( the top sur-
face of the cylinder block should be thorOughly cleaned of ill 'carbon
deposits. Replace with a new one any.valve of which the stem is worn ,
or the head is warped or badly burned. The intake valve fa.ce angle is
30
0
and the exhaust valve face angle i845°.
All old valves to be reused should be ground and assembled to their
original seats. Grind only en:oughto assure a perfect seal.,. Be sure "
to remove a:u traces of grinding compound from valves and seats.
Lightly oil the valves and guides before re~sseml>~. ' '
On some engines the exhaust.valves.are of the.'IIRoto" type, each valve
having a cap under the end of thi:rva.+ve ,stem which pushes up against
the valve spring retaining washer,permitting the valve to rotate
slightly as it opens and closes. When reassembling, .install the cap
on the end of the valve stem before installing the spring retainer
locks. Note tha.t the, ~aust valve retainer locks have a slight taper.
The thilmerecige of thelQck, inu,st face upward. Be sure two locks are
installed on, ,each valve stem. ' The intake valve locks are the single
pin type. If the nRoton ,eihaust valves are properly installed, it
will be possible to tum them in their guides when i'ully open which is
not possible with the conventional type valves.
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