Hi All,
I just discovered this forum and topic and thought I'd reply. I owned a 1939 tiger 100 with the bronze head for many years. I bought it for 325 quid in the late seventies when I was an art student and sold it around the end of the nineties if memory serves. This may not be correct, but when I did the first rebuild and went to buy new valves, guides and springs I was told that the exhaust valves were of the larger, post-war type and guess this could be the difference between the bronze and iron heads. The bike had been raced after the war at Brands Hatch and came with what I was told was a McCandless swinging arm conversion, twin carbs and a finned rear brake hub and drilled sprocket from its racing days. Also 9.5-1 pistons which made it fly until in my ignorance I punched a hole in one using too low grade petrol. I kept it running in many guises with little or no money, but it was incredibly reliable, my only transport, taking me through many winters, snow and all, and even a tour round France. I sold it when I left the country for some years to guy who said he wanted to race it, but I never kept up with him and haven't been to the vintage races for many,many years. Not a huge amount to add to the sum of knowledge on bronze heads, but a rather pleasant nostalgia trip for me. Cheers