The Kawasaki Ninja ZX-4R uses a NGK LMAR9G spark plug. A worn plug causes hard starting, rough idle, and poor fuel economy — replace it on schedule and the engine will thank you.
Inspect the plug every service and replace it at the factory interval or sooner if the electrodes look rounded or the insulator is heavily discolored.
Kawasaki Ninja ZX-4R quick service specs
| Item | Specification |
|---|---|
| Engine oil | 10W-40 (API SG/SH/SJ/SL/SM, JASO MA/MA1/MA2) |
| Oil capacity | 3.0 liters |
| Oil change interval | 7500 miles |
| Chain slack | 25-35 mm |
| Spark plug | NGK LMAR9G |
| Tire pressure (F/R) | 32 PSI front / 36 PSI rear |
| Battery | 12V 8.6Ah (YTZ10S) |
How to replace the spark plug, step by step
- Let the engine cool completely. Remove the seat and fuel tank or airbox cover to reach the plug — check your manual for the exact access steps.
- Blow out the plug wells with compressed air so dirt can’t fall into the cylinder.
- Pull the coil or plug cap, then loosen the plug with a spark plug socket and extension.
- Check the old plug’s gap and condition. Compare the color to a plug chart — white means lean, black and sooty means rich.
- Gap the new NGK LMAR9G to the factory spec, then thread it in by hand to avoid cross-threading.
- Torque to spec with a torque wrench, reconnect the coil or cap, and reassemble everything you removed.
Common mistakes to avoid
- Over-torquing — aluminum heads strip easily. Use a torque wrench, not feel.
- Cross-threading — always start the plug by hand, turning it backwards half a turn first so the threads seat.
- Dropping dirt in the cylinder — blow out the plug wells before you remove the old plugs.
FAQ
What spark plug does the Kawasaki Ninja ZX-4R use?
Use a NGK LMAR9G — same heat range and thread as the original.
Can I use iridium plugs?
Yes — iridium lasts longer and holds its gap better, but check the price difference against how often you ride.
How do I know the plug is worn?
Rounded electrodes, a wide gap, heavy deposits, or a cracked insulator. Hard starting and rough idle are the first signs.
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Dan Heiman
Writer at Helmet Today, covering helmet reviews, fit and riding safety.
