Derbi GPR 125 Racing Workshop Manual page 64

4. Check:
- Movement of the gear change forks (in the guide bar)
Irregular movement => Replace the fork and the bar.
N.B.
IF THE GEAR CHANGE FORK AND THE TRANSMISSION
SPROCKETS ARE FOUND TO BE DAMAGED, REPLACE THE
SPROCKETS THAT ARE SIDE BY SIDE ALL TOGETHER.
5. Measure:
- Warping of the shafts (drive and driven)
Use a support between points and a dial gauge for linear
measurement (1).
Outside that specified => Replace the warped shaft.
6. Inspect:
- Sprocket teeth
Blue colouring/grooves/wear => Replace.
- Sprocket claws
Rounded edges/cracks/pieces missing =>Replace.
7. Inspect:
- Gear change shaft (1).
Damage/warping/wear => Replace.
- Return spring (gear change shaft) (2).
- Return spring (limiter rod) (3).
- Circlip (4).
Wear/damage => Replace.
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