The brake master cylinder is attached to the clutch and brake pedal bracket. Pistons 3 and 4 (pic. 136) activate different circuits. Both pistons take their initial position under the action of springs 7. The movement of the pistons under the action of springs is limited by screws 6. The tightness of the pistons in the cylinder is ensured by four sealing rings 5. The body 2 of the cylinder is closed in front by a plug 1.
In the initial position of the pistons in the cylinder, the spacer rings 9 abut against the screws 6. At the same time, the sealing rings 5 move away from the end surface of the piston grooves and through the resulting gaps the working cavities of the cylinder are filled with liquid from the tank.
When you press the pedal, the pusher moves the piston 4 forward (to the left). The spacer ring 9 ceases to put pressure on the sealing ring 5, and it, pressing against the end of the piston groove under the action of the spring 8, separates the reservoir cavity from the cylinder cavity. This ends the free play of the piston, which on the brake pedal is 3-5 mm.
With further movement of the piston 4, the fluid pressure in the drive cavity of the front wheel brake circuit increases and under its action the piston 3 of the drive of another circuit moves. With good circuits, the pressure in both working cavities of the cylinder will increase equally.