Royal Enfield 570889/B – VB51 Carburettor UCD33 for Bullet 500 BS3 & Thunderbird 500 – Genuine OEM UCD33 Carburettor

The Royal Enfield 570889/B – VB51 Carburettor UCD33 is the genuine OEM carburettor used on select carburetted 500cc UCE models, primarily the Bullet 500 BS3 and Thunderbird 500 BS3. Official parts aggregators list 570889/B as “VB51 – CARBURETTOR UCD33”, confirming it as the factory-spec unit supplied on new vehicles. 

Multiple trusted Indian and export sellers clearly specify this carburettor as “Carburettor UCD33 for Royal Enfield Bullet 500 BS3 (2010–2016)”, while UCAL’s own catalogue identifies UCD33-2 (570889/B) for Thunderbird 500 CC BSIII, cementing its application on these 500cc UCE BS3 carb bikes. 

Built to precise OEM tolerances, the VB51 UCD33 carb ensures the correct air–fuel mixture, throttle response, and idle stability, especially important on long-distance touring and hot Indian conditions. A worn, clogged or locally rebuilt carburettor often causes poor mileage, missing, hard starting and flat spots. Replacing it with a brand-new 570889/B genuine unit restores smooth acceleration and predictable performance.

This carburettor is also widely used in EFI-to-carb conversion projects on 500 UCE engines (especially Classic 500), but those applications should always be treated as conversion use, not factory fitment, and verified with a competent mechanic before purchase. 

Key Features 

• Genuine Royal Enfield OEM VB51 Carburettor UCD33 – Part No. 570889/B 

• Confirmed fitment for Bullet 500 BS3 (2010–2016) and Thunderbird 500 BS3 500cc UCE carb models 

• Constant-vacuum UCD33 design for smooth, progressive throttle and consistent fueling 

• Optimized for 500cc UCE torque delivery, ideal for touring and highway cruising

• OEM-calibrated jets and passages for reliable cold starts, idle and mid-range pull

• Direct replacement for old, seized, or tampered carbs – no jugaad, no re-boring

• Helps reduce misfiring, hesitation, flat spots and poor fuel economy caused by worn carbs

• Compatible with standard airbox and intake adaptor (e.g., 570886 VB51 adaptor to cylinder head) for a complete, leak-free setup

• Backed by Royal Enfield manufacturing quality and UCAL fuel system design 

Compatibility Table 

CHECK PART NUMBER BEFORE PURCHASE

Variants:

• Single Variant:

  • VB51 Carburettor UCD33 – Part No. 570889/B (standard UCD33 spec for Bullet 500 / Thunderbird 500 BS3)

FAQs

Q1. Will this carburettor fit my Bullet 500 BS3?
Yes. Multiple trusted Indian sellers and catalogues list 570889/B UCD33 specifically for Bullet 500 BS3 (2010–2016). 

Q2. Is it also suitable for Thunderbird 500?
Yes. UCAL’s official carburettor range shows UCD33-2 (570889/B) as the carburettor for Thunderbird 500 CC BSIII, confirming factory use. 

Q3. Can I use this for a Classic 500 EFI-to-carb conversion?
This carb is widely used in Classic 500 EFI-to-carb conversions and appears in conversion parts lists, but this is a conversion application, not the original factory setup. Always consult a skilled mechanic and verify jetting, manifold and TCI compatibility before ordering.

Q4. Does it come pre-jetted from the factory?
Yes, the carburettor comes with OEM UCD33 jetting as supplied by Royal Enfield/UCAL for 500cc UCE BS3 models. Fine tuning may still be needed based on altitude, exhaust and air filter. 

Q5. What other parts should I check when replacing the carb?
Inspect the carb-to-head adaptor (570886), air filter, throttle cable and fuel lines. Cracked intake rubbers or clogged filters can limit the benefit of a new carb.