Cylinder Head And Valves - Onan MJA Series Service Manual

CYLINDER HEADS AND VALVES'
DRILL PRESS
BE SURE TO OIL
PILOT OF TOOL
\~~i!ll'"
";'to
~
~d
AFTER CUTTING,
RIND IS EASILY,
REMOVED
MAKE CUT
f.:
FROM EDGE
OF SEAT
G 3.7.D - CUTTING OUT VALVE SEAT WITH ONAN TOOL 420A272
I the pilot to prevent it from seizing in the valve guide. Cut each seat
wn to a narrow rind on edges and bottom and break
it
out with a sharp
:>1..
Be careful not to cut into the counterbore bottom.
loroughly clean the valve seat counterbore and remove any burrs from
~,edges.
If
the counterbore is damaged, it will have to be remachined
r
an oversize seat. Oversize seats are available in .002 in., .005 in.,
10 in. and. 025 in. Otherwise, install new standard size seat inserts.
ive
the
new valve seat inserts into place. Be certain that each seat
sts solidly on
the
bottom of the counterbore at all points. To make
;tallation easier, heat the cylinder head in an oven at 325
0
F for about
~'
hour and cool the valve seats in dry ice.
ce eacbnew seat to a 45
0
angle and width of approximately 3/64 in.
e finished seat face should contact approximately center of the valve
e. Use Prussian Blue on each valve face to check this. Make any
"rections on
the
seat, not the valve face.
'.4.4 Valve Springs. - Check the valve springs on an accurate com ­
~ssion scale. Valve spring data is given in Sect 9. Replace any
ing that is weak, cracked or pitted or has ends out of square.
.5 lNSTALLATION
Push a valve stem oil seal onto each intake valve guide and damp
in. place. Then oil the inside surface of each seal.
NOTE: Plants built before June 1962 had no valve seals.
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