My friend had a 500cc single cylinder DBD34 Gold Star like the one in the picture. I borrowed it occasionally. With it's close ratio box and super high bottom gear (nearly 70 mph) it was a pig in town because you were constantly having to slip the clutch, but when you got onto the open road - oh my word....
How I loved my Constellation. In cafe racer trim it looked fabulous and went like dream. Mind you, the front brake was rubbish and you had to knock it into neutral at traffic lights or the clutch would start to creep.
The BSA Rocket Gold Star was a 650cc twin. They were exciting to look at in cafe racer trim and were fast, good handling bikes but they tended to vibrate at high speed. I nearly swapped my Constellation for one just like the picture above but it's owner kept changing his mind.
My first motorbike. The Matchless G11 was a 600cc twin that was prone to oil starvation of the bottom end and catastrophic seizure when worked hard, as I found out one Sunday evening. I found the replacement parts in Exchange and Mart and the Gentleman selling the parts, upon discovering that I was an impoverished student of Architecture refused to accept any payment. He sent detailed instructions for rebuilding the engine, which ran like a dream until I sold the bike.
The Scott squirrel was a 600cc water cooled two stroke (before the Japanese arrived) I never rode one but my University Lecturer had one. It sounded fabulous. He ruined it's looks in my opinion by fitting a full fairing that sat too far forward. He then fitted a full set of Smiths gauges, - speedometer, tachometer, water temperature, oil temperature, oil pressure and ammeter.