de-restricting an R850 gs
 

Hi all, some advice on my R850gs please. I’ve recently bought a 2000 R850 GS, the bike has been restricted to 33bhp by a previous owner. (It’s an odd UK law for novice riders). Can anyone advise me on how to de-restrict it please? The bike has standard “trumpets” fitted but will still only rev comfortably up to 4000rpm. Anything over 4000rpm is accompanied by a lot of vibration and lack of power.
Words of wisdom welcomely received.
Cheers Rich.