gear have mating "dogs" and "slots." When the
sliding gear moves up against the free spinning
gear, the 2 gears are locked together by the dogs
and slots, locking the free spinning gear to its
shaft. Since both meshed input and output
gears are now locked to their shafts, power is
transmitted from one shaft to the other at that
In 5th gear there are 3 steel balls on the
output shaft spaced 120" apart, which help keep
the transmission from overshooting to 2nd
gear when the rider wants to shift from 1st to
NEUTRAL when the bike is stopped. As long
as the bike is moving and the output shaft is
turning, the balls are thrown away from the
shaft and will allow upshifting to 2nd. When
the bike stops, the ball on top falls into a groove
in the shaft and keeps the gear from sliding into
position for higher gears.
Shift Drum And Fork Operation
Each sliding gear h a s a deep groove
machined around its outside. The curved shift
fork arm rides in this groove, controlling the
side-to-side sliding of the gear and therefore
the selection of different gear ratios.
Each shift fork slides back and forth on a
guide shaft or on the shift drum and has a peg
that rides in a groove on the face of the shift
drum. When the shift linkage rotates the shift
drum, the zigzag grooves move the shift forks
and sliding gears back and forth.
A spring-loaded detent plunger rides in a
cam on the end of the shift drum. This detent
helps keep the drum in the selected gear or in
Refer to Figure 21.
1. Remove the engine from the motorcycle
and separate the crankcase halves as described
in Chapter Four.
2. In the lower engine case, pull out the shift
fork rod and remove the 2 smaller shift forks.
3. Turn the engine case upside down. Flatten
the lockplate and unscrew the shift drum guide
bolt (A, Figure 22).
4. Remove the shift drum detent bolt, spring
and plunger (B, Figure 22).
5. On the clutch end ofthe shift drum, remove
the detent cam circlip and the cam (Figure 23).
6. Remove the large shift fork cotter pin and
guide pin (Figure 24).
7. Pull the shift drum out of the engine case,
taking off the third shift fork as you go.
1. Inspect each shift fork for wear on the fork
arms (Figure 25) and for signs of burning or
cracking. See Table 1 for the minimum shift
fork thickness specification.
2. Make sure the forks slide smoothly on their
shaft and check that the shaft is not bent.
Property of www.SmallEngineDiscount.com - Not for Resale