Thanks everyone again for any help, I am sure you can imagine the trouble I'm having getting info for it (I have a Rothmans NS250F), because:
a) It was never an official UK import
b) It was only produced for 1985-1986
c) The F model was less popular
d) The Rothmans one was a special edition - the Rothmans NS250F has the Astralight wheels of the NS250R, rather than the comstars
So I have a limited edition of a rare bike that was only made for 2 years and never an official import......
I think it shares some common components with the NS400R, so I have downloaded a copy of the NS400R manual from the NS400R site.
I was thinking of upgrading the suspension and wheels to something more modern, but by the time I do that it would probably be cheaper to buy an MC16.... plus my riding is not that hot (I'm not racer, more an urban nutter from my 350LC days) so I wouldn't appreciate the difference and it would end up just being a cosmetic exercise.
I just want a bit more power for point-and-squirt around town, and motorway jaunts which cover most of my riding as I live by the A1 / M1 interchange and work in Liverpool or Coventry / Leamington Spa.
15 / 42 geared it for 125mph which meant it wouldn't rev out in top.
15 / 44 made little difference.
14 / 44 is where it is at now, which I am hoping will have geared it for nearer 115mph revving out in top; it would just about this pull before in 6th without revving out, maybe 8500rpm (but it took favourable conditions, and a long wait from 100mph). This gearing should give better acceleration too.
115mph is more than enough for an unfaired bike!!!
All the best to everyone, enjoy the bank holiday weekend (in the UK)
If anyone is over that way, you might see my bike at Squires in Sherburn-in-Elmet sometime over the weekend - if you live in the North / North East you will probably know it.......