Honda FourTrax Rincon TRX680FA5 2018 Owner's Manual page 156

Brakes
Fluid Level Inspection
Refer to Safety Precautions on page 99.
Front Brake Fluid Level
RIGHT HANDLEBAR
(1)
(1) LOWER level mark
If your inspection indicates a low fluid level, have your dealer add the
recommended fluid.
Do not add or replace brake fluid, except in an emergency. If you do
add fluid, have your dealer check the system as soon as possible.
NOTICE
Brake fluid can damage plastic and painted surfaces. Handle with
care.
With the ATV in an upright position, check the fluid level.
It should be above the LOWER level mark (1). If the level is at or
below the LOWER level mark, check the brake pads for wear
(page 148).
Worn brake pads should be replaced. If the pads are not worn, have
your brake system inspected for leaks.
146 Servicing Your Honda