The brake fluid level must be checked regularly and topped up if necessary.
There is a sight glass on the reservoir of the master brake cylinder with the mark (LOWER); The brake fluid level must be at least this mark. Otherwise, air may enter (airing) into the brake line, which will lead to interruptions in the operation of the brakes. The brake fluid level in the front brake circuit is checked with the motorcycle standing upright.
If the level is at the bottom (LOWER) or below it, it is necessary to add brake fluid to the reservoir (see «Hydraulic brake drive - brake fluid replacement and pumping») and check the condition of the brake pads.