Generac Power Systems GTH1000, Service Manual

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10-2
SECTION 10: CYLINDER & CRANKCASE COVER
Cut a wood block and place inside crankcase to prevent hone from
extending further than 3/4" to 1" (19 mm to 25 mm) below cylinder
bore.
Clamp honing fixture and crankcase securely in a vise at a convenient
work height.
Place hone in middle of cylinder bore. Tighten adjusting knob with
finger until stones fit snugly against cylinder wall. DO NOT FORCE.
Place hone drive shaft in chuck of portable drill and tighten. Be sure
that cylinder and hone are centered and aligned with the drill spindle.
NOTE: The first step in plateau honing requires a 220 grit diamond
metalbond superabrasive stone (such as a Sunnen GMG55). Drill
speed should be 240 RPM at 80 strokes per minute. Lubricate
cylinder liberally to prevent build up on the honing stones. The
second step requires a 800 grit diamond metalbond superabrasive
stone (such as a Sunnen RMG807) at 110 RPM drill speed at 80
strokes per minute.
NOTE: Sunnen lubricating oil (SCC605) is recommended. Automatic
transmission fluid is also an acceptable honing oil. Another accept-
able honing oil can be made by mixing 4 parts 30 weight oil with
1 part kerosene.
45º
Figure 10-4. Cylinder Cross Hatch
CLEANING:
It is very important that the entire cylinder and crankcase be thor-
oughly cleaned after honing.
First wash the cylinder and crankcase carefully in a commercial solvent or
kerosene. Then thoroughly wash cylinder and crankcase using a stiff brush
with soap and hot water. Rinse thoroughly with hot running water. Repeat
washing and rinsing until all traces of honing grit are gone.
Honing grit is highly abrasive and will cause rapid wear to all of the
internal components of the engine unless it is completely removed.
Figure 10-5. Honing Cylinders
NOTE: When cylinder and crankcase have been thoroughly cleaned,
use a clean white rag or napkin and wipe the cylinder bore. If
honing grit is present it will appear as a gray residue on rag. If
any honing grit is evident, re-wash and rinse entire cylinder and
crankcase and check again. When there is no trace of honing grit
on the rag, the cylinder is properly cleaned. Then oil cylinder bore
to prevent rusting.
BEARINGS
CHECK MAGNETO (FLYWHEEL END) BEARING:
Check magneto bearing for damage. Damaged bearings cannot be
replaced. If not damaged, check for wear using a telescoping gauge
and caliper (see Figure 10-6). Measure at several locations. If the
measured diameter is larger than 38.25 mm (1.506”), the crankcase
must be replaced.
The diameter of the crankshaft may also make it necessary to replace
the crankcase. See Section 14 for the crankshaft measurement details.