Well, I ordered the throttle
/brakes at the link below and got them installed today...
After some work on shortening the throttle cable (another thread entirely!)
and a little dremel work tweaking the inner works because like many Chinese cheap parts, it leaves a little to be desired, this thing is AWESOME!
The tweaking to the inner works I am speaking of is removing a little from the inside where the throttle slides. It seems to rub the inner wall a little making it stick and not be smooth. The wires that are attached I think are for brake lights, but I found that if you wanted it to, it could be used as a kill switch that turns off the motor when you apply the breaks. I did not like that, and I cut them off, and stuck with a push button kill switch.
After all of my tweaking and mods, it has a very smooth operation and I love it. My twist throttle that came with my kit was broke when I got it. It would turn past 0 throttle position, and the engine would die. I also found my hand cramping up from holding it. Keep in mind through all of this that I have my engine on an old steel 27" road bike with the ram horn style handle bars, so you lean pretty hard on that twist throttle.
The double brake lever is VERY strong since this is made for ATV's it has a long and very adjustable pull. My bike stops much faster than it did with the stock bike brake levers.
Anyway, just thought I'd share my experience with the thumb throttle/double brake lever.