RCB E4 PLUS (E4+) MASTER BRAKE HYDRAULIC CLUTCH 15MM LEFT HAND

RCB E4 Plus (E4+) Left-Hand Master Cylinder (15mm) is an elite, high-capacity evolution in RCB’s flagship performance control lineup. It is engineered to deliver maximum fluid displacement and precise hydraulic feedback for demanding custom builds.

Outfitted with an oversized 15mm internal bore piston, this premium hydraulic control unit is specifically designed to drive heavy-duty hydraulic clutch conversions on large-displacement motorcycles or to act as a razor-sharp, ultra-responsive rear brake master cylinder on high-performance maxi-scooters. The E4 Plus edition introduces structural body reinforcements alongside a signature external reservoir configuration, offering unparalleled lever adjustment and professional-grade braking power.

Key Features

• Oversized 15mm Pressure Bore: The precision-ground 15mm internal piston moves significantly more fluid per stroke than smaller variants. This makes it the ideal choice for driving dual-piston or large four-piston rear brake calipers, or for cleanly disengaging heavy-duty, multi-spring manual racing clutches.

• Premium Dial-Adjustable Lever Reach: Built with an indexed external adjustment wheel dial. By simply turning the clicker wheel, you can move the resting position of the lever blade closer to or further away from the handlebar grip, allowing for tailored ergonomics that accommodate varying hand sizes or thick riding gloves.

• External Smoke-Tinted Fluid Reservoir: Outfitted with a high-clearance, impact-resistant transparent fluid reservoir tank. This racing-inspired design allows you to visually audit your brake fluid capacity and chemical degradation color at a glance without opening the system to air moisture.

• High-Elasticity Folding Hinge Blade: Engineered with a robust mechanical pivot hinge point. In the event of a low-side track slide, an accidental garage tip-over, or a tight lane-filtering impact, the lever arm folds safely upward rather than shearing off completely at the perch, ensuring you aren’t left stranded.

• Billet-Style Hard-Anodized Finish: Machine-finished with a premium protective coat that shields the assembly against corrosive DOT brake fluid, severe UV fading, and hand sweat oils while maintaining a premium look.

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

Technical Specifications

Dual-System Performance

• As a Hydraulic Clutch Master: When replacing a stiff, binding manual clutch cable on high-torque motorcycles, the large 15mm internal bore provides a highly definitive, crisp friction zone. It creates a complete, clean clutch release with less overall lever travel, making rapid gear changes effortless during high-RPM runs.

• As a Scooter Rear Disc Brake Master: For heavy maxi-scooters upshifting their braking performance, this master cylinder completely eliminates lever sponge. It delivers an immediate, authoritative initial brake bite combined with precise hydraulic pressure feedback, allowing you to trail-brake deep into corners with maximum stability.

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 E4 Plus 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. Set Symmetrical Horizontal Levels: Fasten the master cylinder clamp onto your standard 22mm handlebars at an angle that keeps the fluid reservoir bracket aligned as parallel to the horizon as possible when facing completely straight, ensuring the internal feed port never draws in dry air.