Honda CRF125F 2021 Owner's Manual page 90

Removal and Cleaning:
When the drive chain becomes dirty, it
should be removed and cleaned prior to
lubrication.
1. With the engine off, carefully remove
the master link retaining clip (1) with a
pair of pliers. Do not bend or twist the
clip. Remove the master link. Remove
the drive chain from the motorcycle.
2. Clean the drive chain in high flash-point
solvent and allow it to dry. Inspect the
drive chain for possible wear or damage.
Replace any chain that has damaged
rollers, loose fitting links, or otherwise
appears unserviceable.
Chain:
DID428HD
Never use petrol or low flash point solvents
for cleaning the drive chain. A fire or
explosion could result.
3. Inspect the sprocket teeth for possible
wear or damage.
4. Lubricate the drive chain (page 79).
80
5. Pass the chain over the sprockets and
join the ends of the chain with the
master link.
For ease of assembly, hold the chain
ends against adjacent rear sprocket
teeth while inserting the master link.
The master link is the most critical part
affecting the security of the drive chain.
Master links are reusable, if they remain
in excellent condition, but it is
recommended that a new master link
retaining clip be installed whenever the
drive chain is reassembled.
Install the master link retaining clip so
that the closed end of the clip will face
the direction of forward wheel rotation.
(1) Retaining clip
(1)