Hi I have two spare CB250K heads for my bikes one of which has suffered interesting trauma at some point (no history of engine it came from). I have been asked what the differences are between a CB250K head and a CB350K one. They definitely have different ---286---- and ----287--- part numbers in my 1969 Parts book. The valve part numbers are the same for both models though. Anyone know the differences please? The Picture is of the CB250 (K4 I believe) one with 'trauma'. Anyone knowthe differences between 250 & 350 K heads?