I had a look at the power valves tonight and then at the parts manual and it seems I am missing one washe, either 15 or 16 in the parts book. The one I have doesnt look anything special so it may be wrong. The top cylinder is the same and this means the nut doesnt tighten the front plate up to the valve. It looks like its been that way for a while too.
The end of the valve has a flat machined on two sides and the front plate has slots to allow the plate to be turned a few degrees either way without the valve moving. Is this correct or have ferral parts found their way onto the bike.

Cheers