Thanks for the link, I'll read that with high interest!!!
Any idea of the parts cost for the whole conversion (with used parts like injectors)? That would be interesting to know.
Also, what fuel consumption are you able to achieve? I usually do 5.2L/100km which is equivalent to 45.2MPG for town, suburbs and a 2.3km twisty moutain road which is used for one of the rally of the french montain rally championship, that I take every day to go to work ;-) Best I could achieve was around 4.7L/100km so 50MPG (twisty roads only, no town).
Thanks.
Those are the two most common questions I've been asked about my fuel injection conversion project (the Kawasaki EX250). Tubular has already gone a long way toward answering your fuel efficiency question, at least with regard to raw numbers. The "why" behind any fuel efficiency comparison you might make of two otherwise identical GSF400s, with the already stated observation that there doesn't seem to be a lot of difference in fuel economy between a fuel injected GSF400 and a Carb GSF400, is only worth exploring if you're a real engine technology enthusiast (a gearhead). As Tubular pointed out, a fuel injection conversion is primarily a hobby interest for somebody who really enjoys tinkering and problem solving, with the added bonus of getting to actually ride your creation around afterwards.
But if you're still interested (if you're still reading at this point) I'll go a bit further... (and this is a bit basic, but) an internal combustion engine is, before all else, an air-pump. It's an air-pump of a particular size, in this case 400cc of total volume. That's not going to change when you install a fuel injection system and neither is the engine's operating envelope (the idle to redline numbers). When you begin your reasoning from that point of information you'll quickly see that if the only thing you're changing on an engine is the fuel delivery method there's not a lot of effect available to you (in other words, it's not like adding turbocharging or supercharging which changes the engine's (the pump's) volumetric efficiency).
So when you decide to change a motorcycle from carbs to fuel injection you have to realize that any improvement you might achieve in its performance, in things like fuel efficiency and cold startup and throttle response, will only be marginal gains, but they're often noticeable enough to be worth the effort.
You're fixing the weak spots that invariably exist in any carb's operational envelope: you'll be improving fuel atomization for better combustion (my system runs at 50psi), you'll be improving/smoothing intake tract airflow with a simplified "throttle body" setup, you'll be implementing a much more agile fueling table that eliminates the air/fuel ratio inefficiencies that are inherent in the mechanical switching/overlap of the carb's various fuel input curves (i.e. flat spots in acceleration) and you'll have the ability to tune the fuel/air ratio precisely by taking into account things like Intake Manifold Absolute Pressure, Throttle Position, Throttle Position Rate-of-Change, RPM, Air Temperature, Coolant Temperature, Barometric Pressure and ignition timing.
When you've got all of these things working perfectly the ride is wonderful; the engine response is instant and razor sharp. But in a "blind" side by side test ride comparison you might not be able to guess whether you're riding a really well-tuned carb bike or a fuel injected bike.
As far as the total cost is concerned, I really couldn't tell you with any accuracy. I gather parts a bit at a time: some I've bought new, some I've simply been given by friends, some I've gotten out of junk yards. Because this endeavor is just a hobby for me I don't concern myself with an exhaustive accounting of the costs. I'm sure most people are the same way with their chosen hobbys.
Anyway, it keeps me occupied and happy when I've got spare time and want to concentrate on something technical that I know I can eventually get perfect, unlike the rest of life.
