CYLINDER HEAD ASSEMBLY
CRANKCASE AND END COVERS
Remove all carbon deposits from discharge cavi-
Check for cracks or broken lugs in crankcase and
ties and all rust and scale from cooling cavities of
end covers. Also check their oil passages to make
cylinder head body. Scrape all foreign matter from
sure they are open and clean.
body surfaces and use air pressure to blow dirt
particles from all cavities.
If an oil seal ring is used in the end cover. check
fit of ring in ring groove. There should be 0.008" to
Discharge valves can be dressed by lapping them
0.015" (.203 to .381 mm) clearance at the gap when
on a piece of fine crocus cloth on a flat surface,
placed in the end bore of the crankshaft. If the oil
provided they are not excessively worn.
ring is worn thin or is damaged, it should be re-
placed. Inspect oil ring groove in end cover; if
groove is worn excessively replace end cover or
machine groove for next oversize oil seal ring.
Clean carbon and dirt from inlet and unloader
passages. Use air pressure to blow carbon and dirt
CRANKCASE BEARING BORES
deposits from unloader passages.
With cylinder block installed on crankcase, check
Inlet valves, as in the case of discharge valves,
fit of ball bearings in bearing bores. They must be a
not worn excessively can be cleaned by lapping
tight press fit. The crankcase should be replaced if
them on a piece of fine crocus cloth on a flat sur-
bores are worn or damaged.
Check for cracks or broken lugs on cylinder
Clean thoroughly all oil passages through crank-
block. Also check unloader bore bushings to be
shaft, connecting rods, crankcase, end covers and
sure they are not worn, rusted or damaged. If these
base plate. If necessary inspect passages with a
bushings are to be replaced they can be removed
wire and blow foreign matter out with air pressure.
by running a 1/8" (3.2 mm) pipe thread tap inside the
bushing, then inserting a 1/8" (3.2 mm) pipe threaded
rod and pulling the bushing straight up and out.
Do not use an easy-out for removing these bushings.
Thoroughly clean strainer element, then saturate
it in clean oil and squeeze out excess oil before
INLET VALVES AND SEATS
replacing it in air strainer.
If inlet valves are grooved or worn where they
INSPECTION OF PARTS
contact the seat, they should be replaced. If the
inlet valve seats are worn or damaged so they can-
CYLINDER HEAD BODY
n o t be reclaimed by facing, they should be re-
Inspect cylinder head body for cracks or damage.
Use air pressure to test water jackets of cylinder
head and block for leakage. Replace unit if leakage
Cylinder bores which are scored or out of round
b y more than 0.002" (.050 mm) or tapered more
than 0.003" (.076 mm) should be rebored or honed
DISCHARGE VALVES AND SEATS
oversize, Oversize pistons are available in 0.010,
If discharge valves are worn and grooved where
0.020, and 0.030 (.244, .508 and .762 mm) oversizes.
they contact the seats, they should be replaced. If
the discharge valve seats are worn excessively so
C y l i n d e r bores must be smooth, straight, and
that there is no longer enough metal left to reclaim
them by lapping, the seats should be replaced.
Clearance between cast iron pistons and cylinder
DISCHARGE VALVE SPRING AND CAP NUTS
bores should be between 0.002" (.050 mm) mini-
mum and 0.004" (.101 mm) maximum (Fig. 10). Alu-
Replace all used discharge valve springs and cap