The 570840/A (also known as a “Slow Jet”) is a precision-machined brass component designed for the UC CAL BS29 carburetor. If your motorcycle is struggling to stay running at traffic lights, popping during deceleration, or having difficulty starting, a clogged or worn pilot jet is often the culprit. This genuine OEM part ensures the precise orifice size required for the smooth low-end performance that Royal Enfield motorcycles are known for.
Key Features
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OEM Precision: Direct replacement for the factory-installed jet, ensuring no change in fuel efficiency or idling stability.
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Precision Machined: Made from high-quality brass with a specific #25 sizing to provide the exact fuel flow required for 350cc engines.
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Fuel Grade Durability: Designed to resist the corrosive effects of modern ethanol-blended fuels.
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Improves Rideability: Solves “lean bog” issues and ensures a crisp response from a standstill.
Technical Specifications
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Part Name: Pilot Jet (Slow Jet)
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Part Number: 570840/A
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Carburetor Compatibility: UCAL BS29 Carburetors.
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Compatibility: This part is specific to Carbureted (Non-EFI) UCE models:
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Classic 350 (BS3 and early BS4 models).
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Bullet 350 / 350 ES (Electra).
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Thunderbird 350 (Twinspark carbureted models).
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Maintenance Tip
Pilot jets have very tiny openings that are easily blocked by dried fuel (varnish) if the bike sits for a long time. While they can sometimes be cleaned with a thin wire or carburetor cleaner, replacing the jet with a new 570840/A is the most reliable way to fix idling issues.
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