Main Shaft

Disassembly





1) Remove circlip (1) from main shaft (2) as shown in figure.





2) Pull out 5th gear (1), needle bush (2), needle bearing (3), main shaft bearing (4) and low gear (5) with bearing puller (6) and press (7).





3) Remove synchronizer ring and ball (1).





4) Pull out low speed sleeve / hub assembly (1), needle bearing and 2nd gear (2) from main shaft.
5) Pull off synchronizer springs / keys and low speed sleeve from hub.





6) Remove circlip from front part of main shaft and pull out 3rd gear (1), needle bearing, synchronizer ring and high

Inspection





^ Check clearance "a" between synchronizer ring and gear, key slot width "b" in synchronizer ring and each chamfered tooth of gear and synchronizer ring and replace with new one, if necessary. Also, check gear tooth.





^ Check clearance between fork and sleeve.
If clearance exceeds limit, replace fork and sleeve.





^ Check diameter of main shaft (1) / needle bush (2) and thickness of main shaft (1) / needle bush (2) flanges as shown in figure. If measured value is out of specification, replace them (or it).





Main shaft / needle bush specification (diameter and thickness)





^ Using "V" blocks (1) and dial gauge (2), check runout.
If runout exceeds limit below, replace main shaft (3).





^ Using cylinder gauge (1), check inside diameter of each gear. If its inside diameter exceeds specification, replace it.
^ Check chamfered part of each sleeve for damage and excessive wear, and replace as necessary.
^ Check each synchronizer key and synchronizer spring and replace as necessary.
^ Check splined portions and replace parts if excessive wear is found.





^ Check 2nd gear (1) thrust clearance by using thickness gauge (2). If clearance is out of specification, repress-fit or replace defective part.





^ Check low gear (1) thrust clearance by using thickness gauge (2).
If clearance is out of specification, repress-fit or replace mainshaft bearing and 5th gear.

Reassembly

NOTE:
^ Inspect the parts.
^ Before installation, wash each part and apply specified gear oil to sliding faces of bearing and gear
^ Use new circlips on shaft for installation. Don't reuse circlips.

1) Assemble high speed synchronizer hub (3), sleeve (4), springs (1) and keys (2) according to the following procedure.
a) Slide hub (3) in sleeve (4) so that wider flange side of sleeve (4) and boss side of hub (3) face opposite as shown in figure, also aligning hub slots with key location teeth of sleeve (4).
b) Insert keys (2) in hub slots with depression side of keys face center of hub (3).
c) Install springs (1) to internal circle of key locations with spring end gaps apart at angles about 120 degrees each other, in order to apply spring tension equally to each key.





NOTE: Do not mix high and low speed synchronizer keys as dimensions are different.





1) Install synchronizer ring (1) by matching its key slots to keys as shown in figure.





2) Insert 3rd gear (2), needle bearing (3) and high speed sleeve / hub assembly (4) with synchronizer ring to main shaft (1).





3) Press-fit high speed sleeve / hub assembly (1) with special tool and press (2).





4) Select circlip (1) that will make thrust clearance of clutch hub 0.1 mm (0.0039 inch) or less and install it.





Circlip thickness specification

5) After installing circlip, check that 3rd gear turns lightly.





6) Check 3rd gear (2) thrust clearance by using thickness gauge (1).
If clearance is out of specification, repress-fit or replace.





7) Assemble low speed synchronizer hub (3), sleeve (4), springs (1) and keys (2) according to the following procedure.
a) Slide hub (3) in sleeve (4) with aligning hub slots with key location teeth of sleeve (4).
b) Insert keys (2) in hub slots with depression side of keys (2) face center of hub (3).
c) Install springs (1) to internal circle of key locations with spring end gaps apart at angles about 120 degrees each other, in order to apply spring tension equally to each key

NOTE: Before installing hub (3), sleeve (4), springs (1) and keys (2) assembly to main shaft, there is no specific installation direction on each component. However, when installing assembly to main shaft, gear side of sleeve (4) should face to forward direction as shown in figure.





8) Install synchronizer ring (1) by matching its key slots to keys as shown in figure.





9) Insert 2nd gear (2), needle bearing (3) and low speed sleeve / hub assembly (4) with synchronizer ring to main shaft (1).





10) Press-fit low speed sleeve / hub assembly with special tool and press (1).
11) Check 2nd gear thrust clearance.
12) Apply grease to ball (1) and set it to main shaft (3).





13) Install synchronizer ring (2).





14) Install needle bearing (2), low gear (3) and needle bush (1) to main shaft.

NOTE:
^ Check the cut in needle bush and ball are engaged.
^ After installation, check the synchronizer ring (4) moves in circumferential direction.





15) Press-fit main shaft bearing (1) and 5th gear with special tools and press (2).

NOTE: Bring bearing so that its groove for circlip is in the rear.

16) Select circlip (1) that will make its thrust clearance 0.1 mm (0.0039 inch) or less and install it.





Circlip thickness specification

17) Check low gear clearance.