Royal Enfield Spark Plug WQR8DC (OEM) – Bullet 350 UCE / Bullet 500 UCE / Classic 350 / Electra 350 UCE / Thunderbird 350 / Continental GT 535 – Genuine 572327/B

The Royal Enfield 572327/B Spark Plug (WQR8DC) is a genuine OEM-spec spark plug used across multiple Royal Enfield platforms where correct heat range and reach are critical for smooth starts, stable idle, and clean combustion. Ordering by the exact part number 572327/B is the safest way to avoid common issues seen with mismatched aftermarket plugs—hard starting, misfire under load, reduced mileage, and premature plug fouling. 

This plug is commonly referenced as Bosch WQR8DC (long reach, single electrode, resistor type) in established Royal Enfield parts ecosystems—especially for the Continental GT 535 and Euro-market EFI applications.

It is also a current/updated part number in fiche supersessions: 572327/A → 572327/B, and older “spark plug” numbers like 500904 are shown with 572327/B as the replacement in parts lists—useful when customers search using older workshop bills. 

Key Features 

• Genuine Royal Enfield part number 572327/B 

• Official description: “SPARK PLUG WQR8DC”

• Common OE reference: Bosch WQR8DC (resistor, single electrode; long reach noted in RE ecosystems)

• Supersession supported: 572327/A → 572327/B 

• Cross-reference supported: older listing 500904 shows replacement mapping to 572327/B 

• Improves cold start, idle stability, throttle response when correct spec is maintained (vs wrong plug)

• Quantity per box: 1 in dealer listings 

Compatibility Table 

PLEASE CHECK PART NUMBER BEFORE PURCHASE  

• Thunderbird KS (CDI-2004 / TCI-2005) 

• Thunderbird ES (2005) 

• Bullet 500 (2000) / Standard 500 

Variants

• Single SKU: 572327/B (Spark Plug WQR8DC) 

• Older/related numbers (do not purchase if you already have 572327/B):

  • 572327/A → replaced by 572327/B 

  • 500904 → replacement mapping shown to 572327/B 

FAQs 

1) Is 572327/B a genuine Royal Enfield part?
Yes. It is listed in Royal Enfield microfiche-style catalogs as “SPARK PLUG WQR8DC” under part number 572327/B.

2) My old bill shows 572327/A or 500904. What should I order?
Order 572327/B. Catalog supersession shows 572327/A replaced by 572327/B, and older “spark plug” numbers like 500904 show replacement mapping to 572327/B in parts lists. 

3) Is this the Bosch WQR8DC plug?
It is sold/identified as WQR8DC, and established Royal Enfield parts references list it specifically as Bosch WQR8DC (resistor, single electrode, long reach). Packaging/branding may vary by supply batch, but the key is the correct WQR8DC / 572327/B spec. 

4) Will it fit J-Series 350 (Classic Reborn / Meteor / Hunter) or 650 Twins?
Not confirmed for those platforms under 572327/B in the dealer sources used here, so they are not listed to avoid wrong orders and returns. 

5) What symptoms indicate I should replace the spark plug?
Hard starting, rough idle, misfire under acceleration, reduced mileage, and visible electrode wear/fouling are common signs. Replacing with the correct OEM-spec plug restores baseline performance.