How to Replace Spark Plugs in a Motorcycle

Replace your motorcycle's spark plugs easily.

The motorcycle was invented and became popular around the same time as the automobile in the early twentieth century. Virtually all motorcycles, as of 2010, are powered by internal combustion engines that run on gasoline. This type of engine utilizes spark plugs to ignite the combustion chambers in the engine. Depending on how many cylinders your motorcycle has, you may have between one and six spark plugs to change. Spark plugs can be changed in just a few minutes with simple tools.

Things You'll Need

• Brush
• Shop rag
• Spark plug wrench
• Spark plug gapping tool

Instructions

1. Wait for the engine to cool off completely to avoid getting serious burns from hot cylinders or exhaust pipes.

2. Locate your motorcycle's spark plugs at the top of each cylinder at the front of the bike. Carefully lift up on the base of the spark plug wire where it meets the plug until it snaps free and push it out of the way. Use a small brush or rag to clean the fins and surrounding area around the spark plug of any dirt, gravel or other debris so that it does not fall into the cylinder when the spark plug is removed.

3. Locate your motorcycle's tool kit and extract the spark plug wrench. Place the wrench over the spark plug and carefully turn it in a counterclockwise direction. Remove the wrench once the spark plug has been loosened. Thread the spark plug out of the hole by hand and remove it from the engine.

4. Check your motorcycle owner's guide for the correct spark plug gap, which is the distance between the center electrode of the plug and the grounding strap at the base of the plug, either in millimeters or inches. Find the correct slot on a spark plug gapping tool that matches the correct spark plug gap. Insert the tool in between the electrode and the grounding strap of the plug. Note that if the tool fits snugly, the gap is correct. Adjust the gap by bending the strap slightly in the direction needed to obtain the correct gap.

5. Thread the spark plug into the hole in the cylinder by hand, being careful not to cross-thread it. Tighten the spark plug with the spark plug wrench in a clockwise direction. Push the plug wire back onto the top of the plug until it snaps into place.

6. Repeat Steps 2 through 5 if your motorcycle has multiple spark plugs.

Tips & Warnings

• Use compressed air to remove dirt and debris from the engine if you have access to an air compressor.

• If your motorcycle does not have a spark plug wrench in its tool kit, you can purchase one at any auto parts store.

References

• Why Bike: How to Change a Spark Plug
• Total Motorcycle: Motorcycle Spark Plug Maintenance