The spark plug is located on top of the engine’s cylinder head, tucked under the left-side air-filter box. Access it by removing the left side panel and the airbox, then disconnect the spark plug boot and loosen the plug with a spark plug wrench.
Location basics
The Honda Metropolitan uses a compact 49cc four-stroke engine mounted under the floorboard. To reach the spark plug, you’ll generally remove the left-side cover and the air-filter housing so you can see the top of the cylinder head where the plug sits. The spark plug boot is connected to the plug and may be a little stiff, so twist gently rather than yank.
What you’ll need
Before you begin, gather the tools and parts you’ll use to locate and replace the spark plug.
- Replacement spark plug suitable for a 49cc four-stroke Honda engine (NGK or Denso brands are common; see your manual for the exact heat range).
- Spark plug wrench or a 12mm deep socket with a ratchet and extension
- Screwdrivers (flathead and Phillips) for removing side panels
- Rag or shop towel to clean surfaces
- Anti-seize compound (optional)
- Gloves for hand protection
With these essentials, you’ll be prepared to locate and service the spark plug on most Honda Metropolitan models. Note that exact panel layout can vary by year and market, so consult your owner’s manual if you’re unsure.
How to access and replace the spark plug
The following steps guide you through safely locating and replacing the spark plug. Make sure the scooter is on a stable stand, the engine is cold, and the key is removed before you start.
- Ensure the scooter is cool, then remove the seat and the left-side panel to expose the engine area.
- Remove the air-filter housing to gain direct access to the top of the cylinder head where the spark plug sits.
- Locate the spark plug boot (the rubber connector attached to a thick wire) and gently twist/pull it off the spark plug.
- Using a spark plug wrench, carefully unscrew the old plug counterclockwise and remove it from the cylinder head.
- Inspect the plug for wear or fouling. If replacing, gap a new plug to the manufacturer’s specification (most 49cc Hondas use a standard pre-gap; check your manual).
- Install the new or cleaned plug by threading it in by hand to avoid cross-threading, then tighten to the recommended torque (usually a light snug), and reattach the spark plug boot firmly. Reassemble the air box and left-side panel.
After completing the replacement, start the scooter to confirm normal ignition and idle. If the engine runs rough or misfires, double-check the boot connection and ensure the plug seat is properly tightened.
Maintenance notes
Periodically inspect the spark plug condition during routine service. If you notice fouling, wear, or a persistently difficult start, it may be time for a plug replacement or a tune-up of the carburetor and ignition system. Always replace with the correct part for your model year and consult the owner’s manual for torque and gap specifications.
Summary
The spark plug on a Honda Metropolitan is mounted on the cylinder head, beneath the left-side air-filter box. Access requires removing the left-side panel and airbox, disconnecting the plug boot, and using a spark plug wrench to replace the plug. With the right tools and careful steps, spark-plug maintenance is straightforward and can improve starting and efficiency. Always verify specifications for your specific model year in the manual.