The ultimate guide to dirt bike spark plugs

Dirt bike spark plugs play a pivotal role in the workings of your motorcycle, and depending on whether you ride a two-stroke or four-stroke will depend on how much attention you need to pay them. 

We cover the ins and outs of dirt bike spark plugs in this complete guide!

What is a spark plug? 
In simple terms, a spark plug is a component that ignites the fire that starts your dirt bike engine, delivering a continuous spark that fires once per full revolution on a two-stroke, and every other full revolution on a four-stroke. 

Going deep into spark plug and the technical aspects of them can be difficult to understand, and the further you dig, the more questions you’ll probably ask. But, we will keep things simple throughout this guide. 

When should I replace a spark plug on a two-stroke? 
A spark plug generally needs to be replaced much more often on a two-stroke, which is thanks to oil mixed into the fuel fouling the plug. Fouling the plug can happen through a number of different ways, including carb tuning, fuel mixture ratio, and even just letting the bike idle for too long. 

We always recommended having at least one spare plug when you head to the track, and the easy access of checking the spark plug on a two-stroke means you should be undertaking regular routine maintenance of the component.

A spark plug on a two-stroke is also a good indicator of how the bike is running - if it's lean, the electrode becomes white, and if it's too rich, it will be black and oily. The ideal electrode colour is brown.

When should I replace a spark plug on a four-stroke? 
When it comes to replacing a spark plug on a four-stroke, it’s almost a completely different story to two-strokes. We advise checking your owner’s manual for the appropriate service intervals of your spark plug, however generally speaking, replacing your spark plug once a year will keep you in the safe zone.

How to change a dirt bike spark plug:

Step 1: Firstly you’ll need to remove the spark plug. To do this, remove the spark plug cap followed by loosening the spark plug itself with a socket wrench or spark plug wrench. 

Step 2: Once you’ve taken the old spark plug out, you can insert the new one. 

Step 3: Proceed to tighten the spark plus, but ensure not to over tighten as this will strip the thread in the cylinder head, making for a costly and difficult fix. Also watch out for snapping the spark plug inside the cylinder, which can also occur through over-tightening. 

Step 4: When the spark plug is appropriately tightened, reinstall the spark plug cap.