There should be a tool in your under seat storage that has a spark plug tool.
Underneath the scooter, close the the front of the transmission or directly underneath the passenger foot stands, there should be a ignition wire (it will be a soft rubber wire) connected to the spark plug. Go ahead a pull it off, it comes right off. Then use the tool like a socket to unscrew the spark plug (the screwdriver in the tool kit is used for leverage for you to twist the spark plug tool).
Replace the old plug with the new one, but do not force it in, as the teeth on the plug may strip. Take your time to get it lined up, at this point just using your hand as opposed to the tool might be easier. Once you start screwing it back in, use the tool to tighten it, just tight enough that you can do it with little effort. Just slip the ignition wire back on and you are ready to go.
How to change the spark plug in a 2005 Yamaha Zuma scooter?
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