Vacuum Piston Diaphragm for Harley Keihin CV Carburetor 1988‑2006 Sportster – Replaces Harley 27585‑88 – Throttle Slide Diaphragm Membrane

OVERVIEW

This replacement vacuum piston diaphragm restores proper throttle slide and vacuum valve operation on Harley-Davidson motorcycles equipped with Keihin CV carburetors. Designed as a direct fix for worn or torn factory membranes, this composite repair part brings back consistent fuel delivery and predictable carburetor response. Specifically engineered for the Sportster model family.

ENGINEERING & PERFORMANCE

The reinforced membrane rebuilds precise airflow and fuel mixing inside the Keihin CV carburetor, eliminating the sluggish throttle response and flat spots that come from cracked factory seals. Built to withstand continuous diaphragm cycling and carburetor heat, the durable construction prevents immediate re-tearing after installation. As an exact dimensional match for Harley OEM 27585-88, this component bolts into the carburetor bore without modification and returns the engine to factory tuning parameters.

KEY FEATURES

• Vacuum piston diaphragm designed specifically for Keihin CV carburetors
• Restores accurate throttle slide positioning and vacuum valve actuation
• Treats common symptoms of worn, torn, or punctured OEM membranes
• Direct drop-in replacement for Harley OEM part number 27585‑88
• Precision-calibrated dimensions ensure seamless integration into the carburetor assembly
• Reinforced composite construction built for extended service life and repeated diaphragm cycling

TECHNICAL SPECIFICATIONS

• Brand: Aftermarket Replacement (OEM 27585-88 cross-reference)
• Part Name: Vacuum Piston Diaphragm / Throttle Slide Membrane
• Part Type: Carburetor Maintenance & Repair
• Material: Reinforced Diaphragm Composite
• Supported Years: 1988–2006
• Compatible Harleys: Sportster

FITMENT

• Harley Sportster (1988–2006)

WHY HARLEY RIDERS CHOOSE THIS

Riders reach for this diaphragm when a rough idle, inconsistent throttle return, or weak top-end performance points to a failed carburetor seal. The flexible yet resilient membrane material tolerates the constant sliding friction and thermal cycling inside the CV carb well beyond the lifespan of brittle factory replacements. Because it arrives as a direct dimensional swap for part 27585-88, installation simply strips the old carburetor, presses in the new ring, and returns the bike to baseline tuning without pilot jet adjustments or complex synchronization. This straightforward fix keeps vintage and modern Sportsters running reliably under daily riding conditions.