Measure Twice,
In answer to a couple of your questions. That is indeed a decompression valve. Those little engines had a surprising amount of compression and with the gas in those days it was an at least a once a year job to decoke the engine. You had to pull the head and scrape the carbon/coke off the top of the piston and the head. There were tools to do that so you didn't scratch the piston and cause hot spots on it.
Mostly caused by cheap gas that was made usable by adding lead so I was told. The decompression valve made it easier to start with the kick starter.
With the carbon build up I've had them slide the rear wheel when you dropped the clutch doing a running jump start due the increased compression.
The brake handles are usually installed in the end of the handle bars in Europe and Britain. Just the way they did it.
I did indeed own a James from the early fiftys. Fine little bike and peppy for 98cc. Owned Frances Barnett motorcycles as well and a DOT. They had 198cc and 250cc engines as I remember but that was nearly 50 years ago.
Like to have them back for the $50 and $75 I paid for them. Really like to have the 2 1939 Triumphs that I bought for $150 for the pair.
Dusted them off and replaced the coils and with a tank rinse and carb rebuild/wash out they ran. They were a bear when you got into the cobblestones between the streetcar tracks where I lived.
The springer forks took over and smashed your knuckles against the tank sides as you fought for control and brother I mean smashed. After I was able to get back on the pavement it felt like someone beat them with a baseball bat and looked like it as well.
The guy behind our house was an old motorcycle racer and builder and he took one look at my bandaged hands and said I see you found out about the streetcar tracks. Thanks Reid
Heres some info on the Norman Motobyke
http://www.google.ca/url?sa=t&rct=j...s-27Bg&usg=AFQjCNFMagPxhZu2TWZk9PP4KgcPw9Bz7w
Steve.