RCB S1 MASTER BRAKE HYDRAULIC CLUTCH 14MM LEFT HAND

RCB S1 Series Left-Hand Master Cylinder (14mm) stands as a premier benchmark in RCB’s professional-tier control lineup. Engineered with a true racing pedigree, this master cylinder brings exceptional hydraulic efficiency, crisp feedback, and robust build quality directly to your handlebars.

Featuring a precision-ground 14mm internal bore piston, this premium hydraulic control unit serves as an elite upgrade for motorcycles utilizing a hydraulic clutch system, or as an ultra-responsive rear brake master cylinder for high-performance maxi-scooters with dual-lever handlebar configurations.

Key Features

• Oversized External Tinted Fluid Reservoir: Unlike integrated casting layouts, the S1 Series features a racing-style, smoke-tinted external fluid reservoir tank securely bracketed to the body. This setup isolates the fluid reservoir from heat transfer, prevents bubble formation, and lets you visually inspect fluid level and color breakdown instantly.

• Precision 14mm Hydraulic Bore: The balanced 14mm piston diameter maximizes structural pressure. It moves an optimal volume of fluid per stroke to instantly drive multi-piston rear brake calipers, or decreases physical hand strain by up to 35% when paired with an aftermarket hydraulic clutch slave cylinder.

• Ergonomically Sculpted Forged Lever: Crafted from premium-grade forged aluminum alloy rather than standard cast metals. This delivers a highly uniform molecular structure that resists flexing under heavy compression, providing a stiff, laser-sharp initial lever bite.

• Indexed Multi-Position Reach Adjustment: Features a tactile, click-adjustable adjustment wheel built directly onto the lever hinge. By dialing this wheel, you can micro-adjust the resting distance of the lever blade away from your grip to establish perfect custom ergonomics for your hand size.

• Anti-Snapping Folding Lever Design: Engineered with a durable mechanical pivot hinge. In the event of a track slide, low-side crash, or tight urban filtering scrape, the lever arm folds cleanly upward rather than snapping off at the perch, allowing you to ride your bike back home.

• Built-In Safety Switch: Arrives pre-fitted with a high-durability mechanical micro-switch assembly that plugs smoothly into your vehicle’s factory wiring harness to serve as a rear brake light activator or a clutch-in starter safety interlock.

Technical Specifications

Dual-Application Versatility

• As a Hydraulic Clutch Master: When replacing a stiff, binding mechanical steel clutch cable with a hydraulic slave cylinder conversion, the 14mm internal bore creates a highly progressive, predictable friction zone. Finding neutral becomes effortless, and hand pump is virtually eliminated during heavy traffic or endurance racing.

• As a Scooter Rear Disc Brake Master: For heavy-duty sport scooters like the Yamaha NMAX or Aerox upgrading their braking performance, this master cylinder completely eliminates lever sponge. It delivers an immediate, authoritative initial brake bite combined with precise pressure feedback, allowing you to trail-brake deep into corners with total confidence.

Installation Guidelines

1. Drape Protective Shrouds: Brake fluid acts as a highly destructive chemical solvent on paint and plastic fairings. Before unsealing your hydraulic line or cracking the reservoir cap, completely cover your front fairings, dashboard gauges, and fuel tank in heavy protective towels.

2. Verify Banjo Bolt Threading: The S1 fluid inlet is strictly threaded for an M10 x 1.25mm pitch banjo bolt. Utilizing an incorrect thread pitch bolt (such as an OEM M10 x 1.0mm) will cross-thread and permanently strip out the aluminum housing. Always assemble using the fresh copper crush washers packed in your kit.

3. Perform a Master Cylinder Bench Bleed: Air bubbles naturally rise to the highest point of a hydraulic loop, often trapping themselves directly within the master cylinder piston cavity. Before trying to bleed fluid from the caliper or slave cylinder down below, pump the lever slowly and crack open the top banjo bolt slightly to purge any trapped air pockets first.

4. Secure Reservoir Bracket Alignment: Ensure the external reservoir mounting tab is adjusted so that the smoke-tinted fluid cup sits upright and parallel to the ground when the handlebars are centered. This ensures uniform fluid flow into the main primary port and avoids drawing dry air into the pressure chamber.