Eton VECTOR ST 250 Service Manual page 132

(Dot 3 or Dot 4)
Add the brake oil
Keep oil level at least half of the cup in order to avoid
air in the brake system.
Loosen the bolt to vent the air from brake system.
Tighten the bolt if there isn't any air in the brake system
Tighten torque 40~70kgf-cm
Pull left brake lever slightly in order to extract air from
brake system
Fill the brake oil in the level shown on the cup
when no air comes out
Assemble the cover
132