puchman, please give more info when you ask questions.
The rear (left hand) brake lever on a pre-1981 Express is also the starting lever.
if you are talking about the wind (foot rachet)lever it is ONLY for starting
walk the bike without the engine running and pull that left hand lever. It should stop you cold. if so then you can straddle the bike and push with your feet then try it. Still Ok?, then fire up the bike and try it.
then try the same for the front brake (right hand lever),,,,errrr don't try it with only the front brake and the engine running unless you like doing endos
as you get to know the bike you can find the balance to use both levers at the same time smoothly.