RR lost lots of weight on mine and some inlet porting I did years ago, head and block top skimmed and run with tetraboost rocket fuel added in generous doses . the berger build has a head ported [gas flowed etc] by cylinder head shop with super rocket inlets which they say use a 34mm mikuni on it. I don't think I will be getting 47hp but will be putting some ideas and effort into the engine. many ££££££s worth of goodies waiting in spare bedroom then dropping it in a featherbed, it could be interesting, I will have to wait until brother has built his workshop because he is the engineer and I am on the beer haha, when the pubs open that is