Triumph Trident Tiger Sport Daytona 660 – NGK CR9EIX Iridium IX Spark Plugs x3
Pack of 3 genuine NGK CR9EIX Iridium IX spark plugs, NGK stock number 3521. The three-pack is particularly useful for compatible three-cylinder motorcycles where all plugs are replaced as a set.
What You Receive
- 3 x genuine NGK CR9EIX Iridium IX spark plugs
- NGK retail packaging / identification as shown in the product image
CR9EIX Specifications
- NGK plug code: CR9EIX
- NGK stock / manufacturer number: 3521
- Range: Iridium IX
- Quantity: 3 genuine NGK spark plugs
- Thread diameter: 10 mm
- Thread pitch: 1.0 mm
- Thread reach: 19 mm
- Hex / wrench size: 16 mm
- Heat range: 9
- Resistor type: yes (R in CR9EIX)
- Seat: gasket / flat-seat type
- Centre electrode: fine-wire iridium, approximately 0.6 mm
Why Iridium IX?
NGK uses a very fine iridium centre electrode to improve ignitability while resisting spark erosion. NGK lists CR9EIX as the advanced iridium option for many applications that use a CR9E/CR9EK-family standard plug.
Fitment Guide
- Triumph Trident 660 – 2021 onward: NGK 2025–2026 catalogue specifies CR9EIX stock 3521; 3 cylinders.
- Triumph Tiger Sport 660 – 2022 onward: listed by NGK as Tiger 660; CR9EIX stock 3521; 3 cylinders.
- Triumph Daytona 660 – 2024 onward: NGK catalogue specifies CR9EIX stock 3521; 3 cylinders.
- All three models use a three-cylinder engine, so this pack contains the correct service quantity of three plugs.
Fitment confidence: High – current NGK 2025–2026 catalogue directly lists CR9EIX / 3521 for all three models.
Spark-gap note: NGK catalogue gap: 0.7 mm for the verified Trident 660, Tiger 660 and Daytona 660 applications.
Important: This group is for the 660 three-cylinder family. Do not confuse it with Street Triple 765 models, which NGK lists with CR9EIA-9 on current applications.
Manufacturer / Cross-References
- NGK CR9EIX – primary plug code
- NGK 3521 – NGK stock / manufacturer number
- NGK CR9EK / stock 4548 – standard NGK plug used on many of the verified Triumph three-cylinder applications below; CR9EIX is the NGK advanced iridium option
Vehicle manufacturers may assign their own service part numbers, but CR9EIX / 3521 is the key manufacturer identification for this genuine NGK product.
Before Ordering
- Check the existing spark-plug code or the NGK/Niterra application finder for your exact model and year.
- Do not order purely by engine capacity: motorcycles with the same capacity can use different heat ranges, reach, electrode styles or factory gaps.
- This listing contains three plugs. Confirm your engine requires three if buying a complete service set.
- Do not substitute CR9EIX for CR9EIA-9, CR8EIX, DPR8EIX-9 or other visually similar NGK plugs unless the manufacturer/application data explicitly permits it.
Fitting Note
Install spark plugs into a cool cylinder head using the correct tightening method for the engine manufacturer. Start the plug by hand to avoid cross-threading, and do not alter the factory electrode position unless the vehicle specification specifically requires a gap check/adjustment.
Delivery & Returns
- Free UK delivery with an estimated 2–3 working-day service
- 30-day returns, subject to the plugs remaining unused and in resalable condition