Honda CB1000RA 2021 Owner's Manual page 123

Remove the reserve tank cap and add
1.
fluid while monitoring the coolant level.
Do not overfill above the UPPER level
u
mark.
Make sure no foreign objects enter the
u
reserve tank opening.
Securely reinstall the reserve tank cap.
2.
WARNING
3
Removing the radiator cap while the
engine is hot can cause the coolant to
spray out, potentially scalding you.
Always let the engine and radiator cool
down before removing the radiator cap.
Coolant Adding Coolant
u
119