Thanks, I know fuel injection method would make the engine has better efficiency than carb, but
how big is the difference?
and, if we just use the carb in the motorcycle, we still need some modification here like a gas pedal,
original motorcycle just use use hand bar to control the throttle, you know. do you have any suggestion
on the supplier for gas pedal / carburetor accessories?
Quantifying the fuel usage difference between carb and FI is going to be tricky, but seems like time really well spent. A lot of that will depend on how well it's tuned, as well as the tuning method (speed density, mass air, n-alpha, etc). Finding parts for those carbs should be pretty easy, as they have been making them for well over 20 years. Any motorcycle supplier, like Dennis Kirk, should have parts, or any dealer that can get Keihin parts.
For a gas pedal, that shouldn't be too hard to fabricate. You could either cut the factory cable, or make your own cable. Measure the pull require to open the carbs fully and use that spec to design a pedal. Some aluminum flat stock and a piece of tube will cover most of it.