rattling cover on compensator

hi guys my mate has a 86 fxr and the primary compensator cover spins , when the engine is running it sounds like it has a loose tappet, any ideas, i havent had any experiance of these drives and am in hospital.

There may be a bit lost in translation here.
I don't know of a cover for the compensator. A common problem is the rotor for the alternator which is under the compensator will get loose and spin. When this happens to only fix is to remove it and install a new one. This because as it spins the center hole becomes oblong. I am surprised it is still charging.

ok, thanks chris , i'll let him know, its difficult because i cant see the bike, and that was his description to me, so it could still end up being the loose nut behind the handlebars yet.
regards jib