hello guys thanks for all info, as usual this web site is an amazing source of information, ive now got my 78 CB550 K3 cafe racer running perfect... it seemed to be a multitude of different things,,, first the ignition timing was slightly advanced,, then the air mixture screws all set up different now all set 1.5 turns out,,, and then i purchased a set of carb synchronizers,, set them up, ran the bike and.... wow .... they carbs were way out, spent about an hour setting them up(oh on the PD 46 A carbs the adjustment screws are inside the carb bodies) and now she runs like a dream im so chuffed to get this sorted as my next step was to strip the engine and check the piston rings etc...