Spark plugs are an essential part of a bicycle's ignition system. Voltage is sent from the base of the plug to the plug, jumping from the center electrode to the ground electrode, creating a spark.
This spark ignites the air-fuel mixture in the combustion chamber, causing an explosion that initiates the engine's power stroke. Spark plugs come in different sizes.
Parts of a spark plug, from narrow end to thick end:
●Terminal nut
●Corrugated ceramic profiles
●top insulator sheet
●Hexagonal piece
●metal shell
●Gasket
●Threaded parts
●insulator nose
●center electrode
●Ground electrode
Key measurements for spark plugs:
●diameter
If the spark plug is the wrong diameter, it may not fit into the combustion chamber; it may become damaged; or it may damage the bike's internal components.
●arrival
The length of the spark plug determines how far the spark plug enters the cylinder. It must be the correct distance. Too short and it won't be effective; too long and it can cause pre-ignition, seizure, or even knocking of internal valves.
●Heat resistance range
The thermal range of the plug is printed on the side and is determined by the distance from the tip of the insulator to the ceiling ring. The longer the distance, the hotter the plug; the shorter the distance, the colder the plug. If the spark plug is too hot, it may cause pre-ignition. On the other hand, plugs that are too cold will wear out faster.
●spark plug gap
The spark plug gap is the distance between the center electrode and the ground electrode. The bigger the gap, the bigger the spark. However, when the distance is larger, a larger voltage is required to produce a spark. A shorter distance will result in a smaller spark and possibly incomplete combustion of the air-fuel mixture. Each motorcycle manufacturer specifies the spark plug gap distance for their products.
●Change plug gap size
There are many tools available to help measure and adjust the size of the spark plug gap. Please consult your manufacturer for exact gap size.
Care should be taken when adjusting the gap because the center and ground electrodes and insulators are relatively easy to damage.
How to tell if a spark plug is damaged/not working properly
A spark plug tester can be purchased online for a few pounds. Remove the high voltage lead from the plug. Secure the tester's shield to the spark plug and the rigid end of the tester to the shield on the bike's high-voltage wires, and start the engine. If the spark plug cover receives current, the tester bulb will flash.
Alternatively, you can insert a screwdriver into the spark plug hole and hold it close to a metal part of the bike, then start the engine. If there are sparks between the screwdriver and the bike, the plug is working.
However, these tests only show that the current reaches the spark plug boot. The spark plug may not fire in the combustion chamber - possibly because the chamber is dirty or wet.
Check if your spark plugs are working properly
Remove the spark plug from the combustion chamber while keeping the other end connected to the bike. Hold the spark plug against the motor head or other metal part of the bike. Turn the engine over and if you see sparks, the engine is working. Sparks should be intensely blue, not orange or intermittent.
battery problem
Sometimes the plug doesn't work because the battery doesn't produce enough current. Check that your battery output is at least 12.6V. This can be tested using an inexpensive altimeter online. In the long run, such a purchase will be convenient.
The battery connector should also be well maintained so that electricity reaches the spark plug.
How to clean motorcycle spark plugs
●Carburetor cleaner and wire brush
Most motorcycle owners apply carburetor cleaner to the spark plug tips and then use a wire brush to remove dirt and debris.
●Sandblasting machine
Others purchase special sandblasting devices to clean connectors. However, the black media used in such machines sometimes remains in the spark plugs and is likely to enter the engine. Some users also recommend that ceramic insulators be glazed after sandblasting.
●blowtorch
Some machinists use a blowtorch to burn off debris from the electrodes.
Regardless of which method is used, after cleaning, the spark plug will most likely need to be re-gapted and then reinstalled.
Buy new spark plugs
A cleaned plug may work just as well as a brand new one. However, for those with limited mechanical experience, purchasing a new plug may be a better option. A new spark plug only costs a few pounds.
Your local motorcycle garage will be able to supply and install new spark plugs if required. They may do this as part of your routine maintenance.
Install new spark plug
Remove the spark plug cap. Use an appropriately sized wrench to remove the old spark plug. You may want to plug the hole to prevent debris from entering the engine. Start by installing the new spark plug finger-tight. Use a wrench to tighten further, but be sure not to overtighten as this may damage the plug.
