• Royal Enfield 1040409/C Genuine One Way Valve for BS4 BS6 Models
  • 1040409/C one way valve – Royal Enfield BS4 UCE 350
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UNDER THE HOOD

1040409/C – One Way Valve (Crankcase / Breather Check Valve) for Royal Enfield Classic 350 BS4, Bullet 350 (Std/ES) BS4, Electra 350 BS4, Thunderbird 350 BS4 – Genuine OEM

1040409/C – One Way Valve (Crankcase / Breather Check Valve) for Royal Enfield Classic 350 BS4, Bullet 350 (Std/ES) BS4, Electra 350 BS4, Thunderbird 350 BS4 – Genuine OEM

Rs. 85.00
Rs. 88.00 Rs. 85.00
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This is the genuine Royal Enfield 1040409/C – ONE WAY VALVE used on BS4 UCE 350 models to control crankcase/breather flow. Multiple RE parts sellers list this exact number for Bullet 350 ES – BSIV, and other catalogues say it fits Classic 350, Standard/Bullet 350, Electra 350 and Thunderbird 350 – BS4 years (approx. 2016–2020).

This tiny valve lets air/fumes go out of the crankcase in one direction only and stops hot/oily vapour coming back. A stuck or missing valve can cause oily breather pipes, slight idle instability, or more crankcase pressure. Because this is OEM, it’s made for engine heat and RE hose size, so it will push straight into the breather line and work with the original emission layout. One piece per bike – replace if the old valve is clogged, brittle or lost during hose work.

Key Features

  • Genuine Royal Enfield 1040409/C – One Way Valve. 

  • Designed for BS4 UCE 350 breather/emission routing.

  • Allows airflow in one direction, prevents crankcase backflow.

  • Helps keep breather tube & airbox cleaner.

  • Heat- and oil-resistant OE plastic body.

  • Direct push-fit into the OE hose (no universal adapters).

Compatibility Table (confirmed only)

Model Engine Type BS Stage / Years Status
Classic 350 (UCE) 346cc UCE BS4 (≈2016–2020) Listed as “One Way Valve 1040409/C” for BS4 UCE. 
Bullet / Standard 350 (UCE) 346cc UCE BS4 “Fits in these models: BULLET 350 ES – BSIV.” Same valve for Std 350 BS4. 
Electra 350 (UCE) 346cc UCE BS4 Included in “Classic, Standard, Electra, Thunderbird, all BS4 models” listing. 
Thunderbird 350 (UCE) 346cc UCE BS4 Included in same BS4 UCE group. 






PLEASE CHECKPART NUMBER BEFORE ORDERING

Variants

  • 1040409 (no suffix) → older supply, now 1040409/C live. 

  • Breather hose / crankcase pipe for BS4 UCE – upsell if old pipe is oily/cracked.

FAQs

Q1. What does this valve do?
It’s a check (one-way) valve in the breather line – it lets crankcase gases out but doesn’t let them back in, so the engine breathes better. 

Q2. Will it fit my 2017 Bullet 350 ES (BS4)?
Yes – that exact example is shown by dealer sources. 

Q3. Can I use it on a 2022 Classic 350 (J-series)?
No, J-series uses a different system

Q4. How many do I need?
Just 1 per bike – replace the old one if it’s blocked or damaged.

Q5. What happens if I don’t use the valve?
You can get minor oil mist/backflow into the hose/airbox and slightly poorer crankcase ventilation.

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