I'll try. There are 2 master cylinders. The one on the right just applies the brakes. The one on the left operates a valve that releases the pressure in the transmission so you can rev the motor, while it is still shifted in gear, to operate the hydraulics at fast speed without shifting it to neutral AND also applies the brakes. To do that there must be a valve between the two master cylinders otherwise the brake fluid would just push from one master to the other. There is a piston in the sequence valve that moves to block the line to the right master when pushing on the left brake petal and blocks the valve to the transmission and left master when pushing on the right brake petal. It's similar to a master cylinder inside. If it doesn't work right, it can be rebuilt or replaced. Cleaning won't help. I've noticed when they fail they allow air to get into the brake system.