Honda CRF125F 2021 Owner's Manual page 88

6. Inspect the sprocket teeth for possible
wear or damage.
Damaged Sprocket
Teeth
REPLACE
Normal Sprocket Teeth
GOOD
If the drive chain or sprockets are
excessively worn or damaged, they should
be replaced. Never use a new chain with
worn sprockets; rapid chain wear will result.
78
Worn Sprocket
Teeth
REPLACE
Adjustment:
If the drive chain requires adjustment, the
procedure is as follows:
1. Place a support block under the engine
to raise the rear wheel off the ground.
2. Loosen the rear axle nut (1).
3. Loosen the lock nuts (2) on both right
and left chain adjusters.
(4)
(3)
(2)
(1) Rear axle nut
(2) Lock nut
(3) Adjusting nut
(5)
(1)
(4) Notch
(5) Graduated scale