at Mallory bike festival yesterday, RE had a stand in the paddock staffed by guys from their R and D department: top tip to improve power on 650 twin: bore out inlet tract to diameter of inlet valve( do other details given, and skim head by 1mm, and gives 15-20 more hp.
They also had the flat tracker they use for the UK championship, which has big bore, reworked valve angles ,gas flowing , ( keeps the electric start , so we heard it running) and two stage oil pump with reworked outer cover to supply secondary oil supply to cylinder head for cooling, and a Harris brazed frame, and gives 96hp...!