While the throttle/brake linkage may indeed be set up wrong that is not why the vehicle dies when applying the brake.
Your problem is most likely your idle, more speciffiaclly your idle gap.
When applying the brakes you fully close the carb. If you do not hav a 1mm - 2mm idle gap the engine will be starved for air and stall. The idle screw is usually located near the base of the carb.
Having said that, there are other things that can cause an engine to stall when applying the brakes. Things like broken clutch springs or damaged/sticking clutch shoes will do it too.