9
B. Move piston tight towards camside of engine.
C. Turn engine over in normal direction of travel 2 or
3 revolutions and observe piston during process.
D. Move piston towards driveside of engine and
repeat Step C. If inaccuracies are present due
to machining variations in cases, cylinders or
pistons, top land of piston deck will appear closer
to cylinder wall at one point around
circumference. This means that piston is cocked
in cylinder bore and can be corrected by bending
rod in opposite direction. Figure 5 shows an
exaggerated side view of this condition.
E. Repeat Steps B to D for other cylinder.
NOTE - All engines should be checked upon
disassembly for incorrect piston alignment. This applies
to those which are receiving new pistons as well as those
being completely rebuilt. Observe pistons for wear spots
on sides above top compression ring. If one side near
wristpin is worn clean while side opposite is carboned
up, then piston was not running straight and true in
cylinder bore. Piston will also generally show diagonal
wear pattern on thrust faces of skirts and possibly signs
of connecting rod to wristpin boss contact inside piston.
We feel that not enough emphasis is given to checking
piston alignment in cylinder bore. Proper piston
alignment means connecting rods will thrust to sides
less minimizing added stress on pistons, rings, rod
bearings and other related parts.
7. Breather Timing (1957 to 1976)
NOTES
●
Instances of smoking in early Sportsters led us to
believe that crankcase breather timing was incorrect.
Examination of several engines has shown that
breather timing varies from engine to engine because
of differences in overall width of crank assembly which
changes position of pump drive worm gear on pinion
shaft with respect to pump gear. When engine is
disassembled, breather timing should be checked and
set to XLR specifications.
●
Breather timing should be set so breather valve
opens when front piston is at 20
°
to 25
°
after top center
(ATC) position, and closes when front piston is at 85
°
to 90
°
after bottom center (ABC) position.
●
Crankcase oil scavenging can be greatly improved
on 1957 to 1971 engines by converting to 1972 and later
style breather parts combination. If your engine is 1971
or earlier, we strongly recommend purchase of 1972 and
later pump breather gear, H-D part #26331-72 and
corresponding gear retainer lock ring, H-D part #11002.
These parts are used in place of early pump breather
gear, part #26331-60, because slot in early version is
too wide and requires the removal of too much material
from pump body to achieve desired results. When later
parts are used in early pump, scavenger gear, part
#26315-62, must be installed with flat side of gear facing
retainer lock ring.
To check and correct crankcase breather timing,
perform following steps:
A. Before installing oil pump, turn pump gear
counterclockwise until sleeve hole in gear aligns
with slot in pump body. Place .002" shim in
opening and reverse gear until tight. Scribe
mark across pump gear sleeve and pump body
at small timing notch on top edge of body. See
Figure 6.
Figure 5 Figure 6
Scribe mark
Breather gear just
starting to open
Enlarge closing
side only
(16 paginas)
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