i’d have to pull the cover off my bike to check…but i’m sure it’s just held on by the 10mm bolt in the centre…the big nut locates with 2 tangs into the crank. it’s there just for when you need to turn the moto for doing valves or timing cams.
http://www.cb1100f.net/modules.php?name=Forums&file=viewtopic&t=685
try this link..click on ignition system…it’s for the 900..but it’s the same:D