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The Yamaha R1’s spark plug spec changed across its major redesigns, so “the right plug” depends heavily on which generation you’re riding. Here’s what actually fits the 1998-2008 and 2007-2019 R1s.
| # | Product | Price | Where to buy |
|---|---|---|---|
| 1 | NGK CR9E | $5-$8 each | Amazon · eBay |
| 2 | NGK CR9EIX Iridium IX | $10-$15 each | Amazon · eBay |
| 3 | Denso IU27D Iridium Power | $10-$15 each | Amazon · eBay |
| 4 | NGK LMAR9E-J | $8-$12 each | Amazon · eBay |
The picks, in detail
NGK CR9E
The OEM standard plug for 1998-2008 R1 models, the stock baseline every other option here is compared against.
- OEM standard spec, 1998-2008 R1
- Copper-core electrode
- Direct factory match, cheapest option here
- Shorter service life than the iridium alternatives
NGK CR9EIX Iridium IX
NGK’s iridium upgrade over the stock CR9E for 1998-2008 R1s, a common swap for improved throttle response.
- Iridium center electrode
- Same heat range as CR9E
- Direct fit 1998-2008 R1
- Riders commonly report smoother idle and throttle response over stock CR9E
- Costs more than the standard CR9E
Denso IU27D Iridium Power
Denso’s direct iridium equivalent for the 1998-2008 R1, the main alternative brand to NGK for this generation.
- Iridium Power design
- Cross-references to NGK CR9E/CR9EIX fitment
- Gives NGK-loyal riders a Denso alternative with equivalent fitment
- Exact Denso part varies by R1 sub-year (IU27/IU27D/IU27A) — confirm against your specific year
NGK LMAR9E-J
The direct-fit plug for 2007-2019 R1/R1M/R1S models, a different part number than the earlier CR9E-series bikes use.
- Direct fit for 2007-2019 R1/R1M/R1S
- Laser-welded platinum tip
- Sold in packs for full engine coverage
- Correct match for the crossplane-era R1, not a carryover part from earlier bikes
- Will not fit 1998-2006 R1s — confirm generation before ordering
Buying tips
- R1 spark plug specs changed across generations — confirm your model year before ordering, since the 1998-2008 CR9E-series and the 2007-2019 LMAR9E-J are not interchangeable.
- An iridium upgrade (CR9EIX or Denso IU27D) over the stock plug is the most commonly reported improvement for throttle response on the earlier bikes.
- The R1’s inline-4 takes 4 plugs; replace the full set together for even performance across cylinders.
As an Amazon Associate and eBay Partner, toptenpick.com earns from qualifying purchases. Prices and availability are subject to change.