7-7
Third, use the 46 degree cutter to cut the seat to a width
of .078125 (1.191 mm) (Illust. 7-20). Check the contact
area of a new or reconditioned valve face on a finished
valve seat. Cover the valve face with a black permanent
marker. Insert the valve and turn back and forth in the
seat about 1/8” (3mm) with light pressure. A fine thin
line should appear on the valve face. The contact area
or line should be continuous on the upper 1/3 of the valve
face.
A rigid type hone is recommended to “true” any minor
cylinder irregularities. If the cylinder bore is worn, scored
or out of round more than .005" (.127 mm) oversize, it
should be re-sized to .010" or .020" (.254-.508 mm)
oversize. In some cases engines are built with oversize
cylinders in manufacturing. If the cylinder is oversize,
the oversize value will be imprinted in the top of the
cylinder casting.
If you have determined the cylinders are within tolerance
to hone, proceed as follows. Use a commercially available
rigid hone of the proper size. Chuck the hone in a drill
press with a spindle speed of approximately 600-RPM.
Start with coarse stones and center the cylinder under
the drill press spindle. Lower the hone so the lower end
of the stone contacts the lowest point in the cylinder bore.
Hone the cylinder using lubrication until you have full
cylinder contact.
Change the stones to 380 grit for finish honing. Run the
hone up and down the full length of the cylinder at
approximately 50 strokes per minute. Every fourth or
fifth stroke, move the hone far enough to extend the
stones one inch beyond the top and bottom of the cylinder
bore. At this rate you should achieve a crosshatch pattern
between 35-45 degrees. (Illust. 7-22)
7-20
31
0
TOP
NARROW
46
0
46
0
3/64” SEAT
60
0
BOTTOM
NARROW
SEAT CUTTER
INTERNAL ENGINE
COMPONENT INSPECTION
CYLINDERS
Visually check the cylinders for broken or cracked fins
or a severely damaged cylinder bore. Check all bearing
areas for wear or scoring.
Use a dial bore gauge or telescoping transfer gauge with
a micrometer to accurately measure the cylinder bore
condition. Measure the center of the piston travel area
and approximately 1/2” to 3/4” (12.7 - 19.05 mm) from
the top and the bottom of each cylinder. Measure at 90
degrees to the piston pin, and even with the piston pin at
each level. (Illust. 7-21)
7-22
7-21
MEASURE AT 3 LEVELS
6 LOCATIONS
TOP
CENTER
BOTTOM
NOTE: Always use honing oil to lubricate and cool the
stones. This will also help obtain the best finish.
If cylinder oversizing is needed we recommend boring
the cylinders with a commercial boring bar. Many
Authorized Service Dealers and machine shops offer this
service. Before you choose this method we recommend
costing out a short block replacement, which may be
more cost effective.
Clean the cylinder and crankcase with warm, soapy water
and a stiff brush. Rinse thoroughly with clean water, and
dry. Continue the cleaning procedure until a clean white
cloth wiped on any internal surface reveals no honing
residue or dirt. Coat the cylinder bore lightly with oil.
Replace the piston and the piston rings with the correct
oversize parts as indicated in the parts manual,
microfiche or computer parts look-up systems.
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