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Harley-Davidson Spark Plug Guide: Every Engine, 1936–2026

Harley-Davidson Spark Plug Guide: Every Engine, 1936–2026

Here's the spark plug for every Harley-Davidson engine we have parts for, from the 18mm Knuckleheads and Flatheads up through the Milwaukee-Eight and Revolution Max. Where we have it, you'll find the H-D part number, the NGK, Champion and Denso cross-references, the gap and the torque spec. Click a plug to jump to the plugs we stock for it.

Before you order: pull one of your current plugs and check the number, especially on an older or modified bike. Always set the gap before you install, and use the torque spec from your service manual. Questions? Call us at (978) 710-4913.

Spark Plugs by Engine

Years Engine / Models H-D Plug NGK Champion Denso Gap Torque Notes
1936–1947 Knucklehead EL/FL, Flathead W / U / UL / G 18mm plug — — — See manual See manual These engines take 18mm plugs. Some '37–'48 UL flatheads use 7/8" plugs
1948–1974 Panhead ('48–'65), early Shovelhead ('66–'74) See plugs we stock — — — See manual See manual
1957–1978 Ironhead Sportster See plugs we stock — — — See manual See manual
1975–1984 Shovelhead FL / FX 5R6A (32342-04) BPR5ES RN12YC W16EXR-U11 .038–.043" 18–22 ft-lb H-D lists 5R6A for late '78–'84 Shovels; check your plug on earlier bikes. Hot and cold versions available
1979–1985 Ironhead Sportster See plugs we stock — — — See manual See manual
1984–1999 Evo Big Twin 1340 – Softail, Touring, Dyna, FXR 5R6A (32342-04) BPR5ES / BPR5ES-11 RN12YC W16EXR-U11 .038–.043" 18–22 ft-lb 14mm plug
1986–2022 Evo Sportster 883 / 1200 (carbureted and fuel injected) 6R12 (32362-04A) DCPR7E RA8HC XU22EPR-U .038–.043" 12–18 ft-lb 12mm plug
1999–2017 Twin Cam 88 / 96 / 103 / 110 – all models incl. CVO 6R12 (32362-04A) DCPR7E RA8HC XU22EPR-U .038–.043" 12–18 ft-lb Same plug every year
2002–2017 V-Rod (Revolution engine) 10R12A (32335-04) DCPR8E — XU24EPR-U .035" 17 ft-lb 12mm plug
2017–2026 Milwaukee-Eight 107 / 114 / 117 6R10 (31600012) CR9E RG6HCC U27ESR-N Check manual 89–133 in-lb 10mm plug, 4 per bike (2 per cylinder). Torque is in INCH-pounds
2015–2020 Street 500 / 750, Street Rod 6R10 (31600012) CR9E RG6HCC U27ESR-N Check manual Check manual 10mm plug
2021–2026 Revolution Max – Sportster S, Nightster, Pan America 31600190 — — — Check manual Check manual Use the H-D plug or a direct Rev Max replacement

Spark Plug Tips

  • Different sizes, different eras – Knuckleheads and Flatheads use 18mm plugs, Shovels and Evo Big Twins use 14mm, Twin Cams and Sportsters use 12mm, and Milwaukee-Eights use 10mm with two plugs per cylinder. They don't interchange.
  • Watch the M8 torque – the M8's 10mm plug is torqued in inch-pounds, not foot-pounds. Over-tightening can strip the threads in the aluminum head.
  • Gap every plug – check the gap even on "pre-gapped" plugs. Plugs get knocked around in shipping.
  • Iridium upgrades – iridium versions like the NGK DCPR7EIX (Twin Cam / Sportster), BPR5EIX (Shovel / Evo) and CR9EIX (M8) last longer than standard plugs. They're a direct swap.
  • Install cold – change plugs with the engine cold, thread them in by hand first, and use a dab of anti-seize if your plug maker recommends it.
  • Read the old plugs – tan is good. Black and sooty means running rich, white or blistered means running lean or hot.

Spark Plugs We Stock

Here are the plugs we carry for each engine. Check the product page for current pricing and stock.

Knucklehead & Flathead – 18mm

Panhead & Early Shovelhead (1948–1974)

Ironhead Sportster (1957–1978)

Shovelhead 1975–1984 & Evo Big Twin 1984–1999 – 5R6A

Ironhead Sportster (1979–1985)

Twin Cam & Evo Sportster – 6R12

V-Rod – 10R12A

Milwaukee-Eight & Street – 6R10

Revolution Max – 31600190

Need Help?

Shop all Harley spark plugs & wires, or call us at (978) 710-4913 or email sales@deadbeatcustoms.com with your year and model.

4th Oct 2026 Steve B.

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