Thunderbird 900 cutting out

Hi hoping someone can help, I have a 1995 Thunderbird 900 18000 miles. Had it for about 6 weeks and local 30mile ish rides have presented no problems. Took it on a longer motorway cruise to the Yorkshire Pudding Rally this weekend and after about 40 miles (30 at motorway speeds) the engine simply cut out at about 70mph! Luckly I was able to cruise on to the hard shoulder. First thought was fuel so took the cap off and could hear fuel. Cap back on Switched to reserve and it started on the button less than 2 min after cutting out, found petrol station but only took 7.5L to fill up so was only 1/2 empty at time of cut out. Finished remainder of ride with no issue. Ride home no issue but as I stopped 1/2 way for a coffee (feeling a little rough after a great rally) may not have reached same fuel level or temperature. Any ideas what it could be if not fuel related? I'll check the fuel lines for sludge etc but it has left me feeling nervous given there was absolutely no warning just simply cut out dead! Thanks in advance.
Pete.

 

Thanks guys I'll try the redex (may even try some myself might clear the old artries ). I'm really hoping it's something simple like a fuel blockage. I'll work my way through the system. I love the bike and don't want to fall out with it over something so annoying!

 

Thanks Wayne will do - Sorry if a bit thick but what is a cdi box?

 

Thanks Wayne I'll be having a look this week, not had chance in last few days.