Im just replacing mine as i speak and want to know which was the cog goes on the main pulley drive. The top cog has a guide rail that is closest to the charger and the one on the main drive had the guide rail away from the charger. Will get a pic to be more clear.
the main pulley one has a big keyway, the top has a small one - but doesnt need to come off. If it has then you need to loctite the bolt on.
guide on the inside on top one, outside on bottom - as you described
Like this
(http://i443.photobucket.com/albums/qq157/jezza-3/008.jpg)
Not this
(http://i443.photobucket.com/albums/qq157/jezza-3/009.jpg)
Top ones fine