RCB S1 PISTON 14MM Bocket for S1 MASTER BRAKE PUMP

RCB S1 Piston 14mm is the official internal repair and maintenance component for the RCB S1 Forged Master Brake Pump. It is a precision-engineered kit designed to restore the hydraulic pressure and “snap” of your master cylinder if it begins to leak or feel “spongy.”

Unlike universal kits, this is a dedicated Forged Series component, ensuring it meets the high tolerances required for radial-pump performance.

Key Features

• Forged Compatibility: Specifically designed for RCB S1, S2, RS-1 & S1-FL Master Brake Pump series.

• High-Grade Material: The piston is typically crafted from lightweight aluminum with a specialized coating to reduce friction and wear against the master cylinder wall.

• Complete Seal Set: Most kits include the main 14mm piston along with high-pressure rubber seals (O-rings/cups) and a return spring to ensure a complete hydraulic seal.

• Restores Performance: Over time, brake fluid can degrade rubber seals. This kit is the standard solution for fixing a “leaky” master pump or one that is losing pressure under hard braking.

When do you need a Piston Replacement?

1. Fluid Leaks: If you see brake fluid seeping from the area where the lever pushes into the pump body, your piston seals are likely worn.

2. Spongy Lever: If you have bled your brakes but the lever still feels soft or moves to the handlebar with little resistance, the piston may be allowing fluid to “bypass” the seals.

3. No Return: If the lever is slow to return to its original position after you let go, the internal return spring or piston surface may be compromised.

Comparison: 14mm vs. 17mm Piston Kits

It is vital to use the correct size.

• 14mm Kit: Used for the standard S1 pumps designed for 1-piston or 2-piston calipers (common on underbones and 150cc–300cc bikes).

• 17mm Kit: Reserved for the high-volume S1 pumps used with 4-piston calipers or dual-disc setups.

Maintenance Tip

When installing the new 14mm piston, always lubricate the new seals with fresh DOT 4 brake fluid before sliding them into the bore. Inserting them “dry” can cause the rubber to tear, leading to immediate leaks.

Safety Warning: Rebuilding a master cylinder is a critical safety task. If you are not comfortable bleeding brakes or working with internal snap-rings, it is highly recommended to have a professional mechanic install the kit for you.