This article was contributed by Ifixjets (Brian).

Here are a few photo's showing how I reached the Spark Plug. It took me all of 10 mins to change the plug. It's not very difficult to reach it, and you can't see the plug at all, just the plug boot and wire. Removing the plug itself is by feel. It is also a good idea to use some compressed air to blow away any dirt and debris out of the SP recess after you remove the plug boot. That way nothing will fall into the cylinder after the plug is removed.

Just reach around the cylinder head and grab hold of the boot, pull if off.

My finger is on the wire/boot. When you pull it off (it may take some wiggling) don't pull on the wire itself, grab a hold of the boot.

Use the plug wrench from the Vespa tool kit, it is much easier and was made to get into this tight spot, the open end wrench works best too.
Wasp Rider wrote:
I remove the spark plug the same way as ifixjets. I did it quite often when I first put on the PM exhaust to check the plug colour and see if rejetting was required. Anyway, see the phillips screw in the last picture, just above your hand...well if you unscrew that, there is a block connector under it, it is attached to the spark plug boot and lead. You can move this out of the way and this will give your hand more room to get at the plug. Hope this helps everyone I know our Vespa mechanic liked it.