It sounds as if the linkage either needs to be adjusted, or something is seized up which is fairly common. If you have a safe way to go about doing it, I would lift the machine up for easier access underneath and spray lubricant on the moving brake linkage parts and see if you can work anything loose, assuming something is seized.
Here is a diagram of the linkage. If it needs adjustment and from what I've gathered, it appears you can make the adjustment(s) at #1B.
Looks like there might have been two types of brakes used on those. One being a drum style and the other being a wet disc type. Below are the images I found at the link above of them. You can also find images there of the clutch and brake pedal linkages.