Spark plugs might be small, but pop them in a motorcycle engine and they’ll propel you forward like little firecrackers. As long as they’re well-maintained, spark plugs will help your motorcycle start faster, run smoother, and perform at its best. But how do you keep them in top condition? Plus, even more pressingly, how do you spot the signs of bad spark plugs — and know when it’s time to replace them?

We’re about to tell you everything you need to know about cleaning and maintaining motorcycle spark plugs. We’ll also give you pointers on how to spot wear and when to swap your spark plugs out for new ones.

Why Spark Plug Maintenance Matters

Motorcycle spark plugs ignite the fuel-air mixture in your engine’s combustion chamber. On a good day, when they’re clean and properly operational, you can count on their power delivery and throttle response. But when dirty or worn, you may notice poor performance, sluggish starts, or even misfires.

How to Clean Motorcycle Spark Plugs

Keeping spark plugs clean is a surefire way to extend their life. Here’s how to do it right:

1. Safely Remove the Spark Plug

Never perform this step while the engine is still warm — your first step is to turn off your bike and wait for it to cool. When safe, gently remove the plug using a spark plug socket and ratchet. Whatever you do, don’t inflict damage on the ceramic insulator or threads.

2. Inspect Before You Clean

The next question is whether your spark plug needs cleaning or replacing. To know for sure, check whether it’s dirty and carbon-fuelled, or worn-down and oily. If it’s in the former condition, it needs cleaning; if it’s in the latter condition, it’s time to replace it.

3. Clean the Electrode

If you’ve determined that your spark plug needs cleaning rather than replacing, your next step is to gently scrub carbon deposits off the electrode using a wire brush or spark plug cleaner. Pro tip: Avoid using abrasive materials that may damage the metal. Also, a little brake cleaner can do the trick if you come across stubborn grime. Finally, before reinstalling the spark plug, check that it’s 100 per cent dry first.

4. Check the Gap

Check the spark plug gap using a feeler gauge before reinstalling it. An incorrect gap can affect combustion and performance, so knowing the correct specification is essential — check your bike’s owner’s manual.

5. Reinstall the Plug

Once cleaned and checked, reinstall the spark plug, being careful not to overtighten it. Ideally, you’ll use a torque wrench — spark plugs only need to be snug, not cranked down.

Signs of Bad Spark Plugs

Spark plugs have limited lifespans, and cleaning can only go so far. Here are some common signs of bad spark plugs:

• Difficulty starting the engine
• Engine misfires or rough handling
• Power loss or poor acceleration
• Increased fuel consumption
• Black, oily, or blistered plug tips

If you notice any of these signs, even after cleaning, the spark plugs have had their day and are ready for replacement.

How Often Do You Need to Change Spark Plugs on a Bike?

The general rule is to change your spark plugs every 8,000 to 16,000 kilometres, but this number varies depending on your bike, riding conditions, and the type of plug used. If you ride hard, off-road, or in dusty environments, you should change them more frequently.

Checking your engine regularly — for example, every couple of oil changes — can help you spot issues before they leave you stranded.

How Do I Choose a Spark Plug for My Bike?

Your first port of call is your owner’s or workshop manual, which should contain manufacturer recommendations about the correct part number, thread size, heat range, and electrode material. Of course, if your engine has been modified (e.g., with nitrous oxide or a higher compression ratio), the manufacturer’s recommendations may be unhelpful. If you’re stuck, hit up a trusted mechanic or our customer service team.

Generally speaking, whether a spark plug is right for your bike will depend on:

• Your bike’s make and model
• Engine type and size
• Heat range and electrode model
• Your typical riding style and conditions

Get Your Motorcycle Spark Plugs at Motoxparts

If you’re here, chances are you need some motorcycle spark plugs. Luckily, Motoxparts is home to the highest-quality bike engine parts in New Zealand. Shop motorcycle spark plugs in our online store, or contact the Motoxparts team with your burning questions — like, ‘How do I choose a spark plug for my bike?’. Whether you need new spark plugs or something else altogether — a new pair of riding boots, perhaps? — we’ve got all your bike-related queries covered.