The RCB S1 Piston 17mm is the high-volume internal repair kit for the S1 Forged Series radial master cylinders. While the 14mm version is for standard setups, the 17mm piston is specifically engineered for high-performance braking systems that require moving more fluid to actuate larger calipers.
Key Features
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Forged Series Compatibility: Specifically designed for 17mm master pumps.
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Precision CNC Finishing: The piston is machined to extreme tolerances to ensure a perfectly smooth stroke, reducing friction and improving the “bite” feel at the lever.
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Complete Maintenance Set: The kit typically includes the 17mm aluminum piston, high-tension return spring, and specialized nitrile rubber seals to prevent pressure loss.
Why Choose the 17mm over the 14mm?
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17mm (High Flow): Choose this rebuild kit if your master pump is paired with a large 4-piston caliper or a dual-disc system (common on bikes like the Ninja 400, R3, or Interceptor 650). It displaces more fluid per stroke.
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14mm (Standard): Only for standard 1 or 2-piston calipers. Using a 17mm piston on a small caliper will make the brake lever feel incredibly “hard” with almost no travel.
Installation & Safety
Rebuilding a 17mm radial pump is a precise task. To ensure success:
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Cleanliness is Key: Use only Brake Cleaner to prep the bore. Never use petrol or oil, as it will destroy the new rubber seals instantly.
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Lubrication: Coat the new rubber seals with fresh DOT 4 brake fluid before inserting the piston into the master cylinder body.
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Snap Ring Security: Ensure the circlip/snap ring is fully seated in its groove to prevent the piston from ejecting under pressure.
