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Clearance between the piston and cylinder must be measured at the
bottom of the piston skirt thrust face. Refer to Chart, Fig. 37,
for proper clearance. The thrust faces on the piston skirt are 90°
from the axis of the piston pin hole.
In
reassembly; use a ring compressor and stagger the piston
ring gaps 90° apart around the piston. Oil the piston, rings, wrist
pin, rod bearings and cylinder walls before assembly.
Note:
Mount piston and rod assembly with the stamped number on the connecting
rod bolt boss facing toward the open end of the crankcase. Assemble
connecting rod cap in like manner so that the two numbers are on
the identical side. Turn crankshaft to lower end of stroke and tap
piston down until rod contacts crank pin. Mount dipper so that cap
nuts are accessible from open end of crankcase. Tighten connecting
rod nuts to 22 foot pounds torque.
PISTON
RINGS (Fig's. 38 and 39)
If a ring expander tool is not available, install rings by placing
the open end of the ring on piston first, as shown in Fig. 38.
Install bottom ring first and work up to the head of piston, installing
top ring last. Spread ring only far enough to slip over piston and
into correct groove, being careful not to distort ring. A
pit mark, or the word 'top' is stamped on
the rings, to indicate the correct placement of the rings on the
piston: Scraper ring must be mounted with scraper edge down, otherwise
oil pumping and excessive oil consumption will result.
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CYLINDER
BLOCK
Clean all dirt and foreign deposits from between the cylinder
block fins.
The block
does not have to be removed unless the cylinder bore is worn more
than .005 inch oversize. The block should then be
reground and fitted with oversize piston and rings. This work
should be done at an authorized 'Wisconsin Service Station'.
In reassembly:
tighten the four cylinder block mounting nuts, 40 to 50
foot pounds torque. The capscrew in valve spring compartment
should be tightened to 32 foot pounds torque.
CAMSHAFT
and VALVE TAPPETS (Fig. 40)
TIMING MARKS (Fig. 41)
To prevent tappets from failing out and becoming damaged when
camshaft is removed, turn crankcase over on its side as shown
in Fig. 10. Push tappets inward to clear cam lobes and remove
camshaft.
Figure 40
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Figure 41
Remove
tappets; check face for scuffing and inspect body for wear. Body
diameter of .6245 / .6235" has a clearance of .0005 to .0025"
in guide hole.
In
reassembly: Tappets must be inserted in crankcase before
camshaft is assembled. Mount camshaft so that timing mark on cam
gear matches up with marked gear tooth on crankshaft gear. See
Fig. 41. If valve timing is off, engine will not function properly
or may not run at all. Be sure thrust spring is in place in end
of camshaft, before mounting gear cover.
TAPPET
ADJUSTMENT (Figure 42) Tappet adjustment can be made immediately
after assembling the valves, springs and locks, see Fig. 42. With
the tappets in their lowest position and the engine cold, the
clearance should be:
inlet
- .007 inch
exhaust - .016 inch
Caution:
Be sure exhaust tappet is not riding on compression release spoiler
cam. To check tappet clearance on an assembled engine; turn crankshaft
so that take-off or flywheel keyways are in a 12 o'clock position,
and on compression stroke. Observe position of valve stems in
the inspection compartment. Both valves should be in their lowest
position (closed); proceed to check clearance.
Figure 42
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Figure 41
COMPRESSION
RELEASE (Fig. 43)
The automatic compression release is incorporated with the engine
camshaft, and with proper engine maintenance should operate trouble
free, with a minimum of wear.
While
cranking engine, a spoiler cam holds the exhaust valve slightly
open thru a portion of the compression stroke. This condition
reduces the compression pressure, allowing the engine to be turned
over faster and with less effort. After the engine starts and
speed reaches 650 R.P.M., the flyweight places spoiler cam in
an inoperative position and normal compression is returned to
combustion chamber.
BREAKER
PUSH PIN and BUSHING (Fig. 44)
Push pin for breaker am should be removed, inspected for wear
and replaced if necessary. In reassembly: Mount assist spring
under head of push pin and insert pin assembly into guide hole,
with spherical end of pin toward camshaft striker plate, see Fig.
44.
If clearance between new push pin and bushing is excessive, replace
bushing. Ream I. D. of bushing .2785 to .2790 inches after pressing
in place. Mount bushing to crankcase with LOCTITE if necessary.
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Figure 44
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Wisconsin S-10D, S-12D,
S-14D 
