I found this whilst Browsing and thought I'd share so mayben it might help someone along the way
Pull the pipe out.
Be careful not to damage the gasket between the cylinder head and the exhaust; if you do, you will have to replace it; it won't do to have gases escaping from this union.
Plug one of the openings of the exhaust; you have to create a good seal here, sometimes wine bottle corks work well, but don't use any tape, as the cleaning chemical you will be using will break it down completely. Now, spray a whole can or two of brake cleaner inside, then plug the other opening; sometimes there is a secondary opening on the side of the pipe, or a "slave tube", plug these as well.
Slosh it around and let it sit for a while; then, slosh it around again and let it sit in a different position; do this as many times as you can and if possible allow the chemical to work overnight. While you are waiting, you can take a look at the exhaust port on the cylinder head, if there is build up here too, clean it up VERY CAREFULLY with a little brake cleaner and a rag; turn the engine so that the exhaust port is covered by the piston, that way you'll avoid pushing deposits into the chamber; don't use a screw driver, as you could damage the piston.
here is another way but I prefer what youve already read above..
http://www.scootertherapy.com/mufflercleanpage.html
