I've done a couple of Fazers to date
 
Pictures of different front ends below
 
 

If the nut is secure and you're not intending changing the front sprocket I'd leave it where it is.
 
If the bike has never had a front sprocket change and the nut hasn't been affected by sprocket chatter (and as far as I can tell most bikes aren't affected) then you will find that the nut is very tight and difficult to undo.
 
First time I changed the front sprocket I ended up using a 240V impact driver.  I think it cost around £45.00 from Machine Mart.
In any event it worked a treat, but don't use one to tighten the nut up unless it has torque settings.
 
When I put a new sprocket on I used 'bearing fit' on the output shaft splines and locktite on the nut along and a smear of grease between the tab washer and the sprocket.
 
 
If there is a problem with the nut and it's not tight, consider this:
 
I reckon the reason why the problem with the front sprocket nut exists is as follows:
 
Minor play between the sprocket and shaft, due to shaft or sprocket being machined out of tolerance.
Nut tightened up on the sprocket.
Sprocket moves fractionally back and forward, and because the nut is tight to it, so does the nut.
Nut threads wear out as do the shaft threads.
 
Possible solution:  Grind down the over-lap of the nut so it tightens up on the shaft and not on the sprocket.
In essence it should be flush with the sprocket but not tightening up against it.
Ideally make sure there's a layer of grease between nut / security washer / sprocket.
 

 

Replica CX 500 spark plug caps fit and you can get them from M & P accessories and they were cheap when I bought them, which is about five years ago. 
 
Oh and the rubber seal off the original ones fitted on the CX 500 ones.

To Darrsi
 
I've read it...... it's a good article, but it doesn't fit with my personal experience, and so all I can say is:
Sleeving down the outlet of the Motad system brought back the power band, made the plugs the right colour and dropped the exhaust gas temperature. 
 
The odd thing is you can actually see the 'pinch point' in the original exhaust system, and it's difficult to imagine Yamaha putting that in if it wasn't needed.   
 
 

If you change your exhaust headers make sure the restrictor point of the new set is similar in overall opening size to the original set.

The original outlet is:  35mm – 43.5mm diameter externally at its most restricted point.

I’m not sure what the wall thickness is but I reckon it must be somewhere between 1.0mm and 2.00mm, my original pipes are still in good condition and I was loathe to saw them up to find out.

In any event the Motad replacement header system outlet pipe is has a clear open area of 1364sqm.  Whereas the original outlet is restricted to somewhere between 962sqm and 1075sqm.

When I fitted the Motad headers the power band almost evaporated and a gas analyser showed it be running far too weak, this being supported by the plug colour.

A further test was done by a lazer temp gauge on the exhaust clamp bracket of both original and new pipes and this showed the exhaust gas temp had risen.

To solve the issue the Motad pipe was sleeved down first to 1075sqm which improved things no end, and finally down to 975sqm, which seems to be better.

Plugs were checked and exhaust gas analysed and the results were as good as I could get them.

However if you don’t get the right back pressure the engine will run too weak and it is possible that you may end up damaging the exhaust valve edges and seats.
 
The photo below is the restrictor point in the original header set.

Some stainless steel headers don't offer enough back pressure, Motad for instance; and you need to sleeve them down at the collector point.
 
The Motad collector pipe measures 1364sqm whereas the original collector has an open area of 962sqm (based on a 2mm wall thickness) at its pinch point.
 
You can see where the original back pressure adjustment (pinch point) was made point on the standard header pipes collector point.