I'm all for EFI on 2 strokes as the volumetric efficiency does change alot more through out the rpm range than 4 strokes, something you cant tune out with a carb.
While people don't seem to give them much credit - modern carburation systems are highly advanced.
To top that off - they do something by fundamental design that many efi systems do not; meter what happens inside the engine upstream.
Now - MASS air flow style efi systems DO measure this, at a cost - flow hindrance and complexity of system.
On high performance two strokes, we also depend on the inlet system for a resonance to help boost output. This can be hindered via a mass sensor. On top of that, depending where the sensor is located, two strokes experience a serious flow reversal problem in some instances.
This is also hard to account for.
EFI has been tried at the highest levels of two stroke racing by various teams, and thus far has not truly suceeded. My "sources" tell me it came down to a few highly dynamic, and difficult reasons to overcome. One being the bulk pipe temperatures. This means that if an engine were loaded on a long up hill in a situation where the rpm stays basically constant, the longer it is run - the hotter the average pipe temps get.
The change in pipe temperature influence the scavenging pulses of the pipe, and changes power output. It's hard to adjust an FI system for this without a mass air flow sensor..but a carb adjusts automatically on demand (via metered velocity).
Also, when a two stroke is coming on and off the pipe, the fuel delivery requirements are all over the place! It's hard, again, for fi to keep up with this. Carb's just do it..
For the road racers, it came down to this scenario - when your leaned over doing 120mph around a fast corner, at max lean angle, and you are in a controlled slide - it's important that when you need that right hand connected to that rear wheel DIRECTLY and INSTANTLY with complete predictability you have that connection. A hair too much throttle and your highsided up on your ass - crying for mommy.
With the FI systems tried - they never got to the point where rider input was perfectly matched with what the bike did. This made it hard to ride.
For about 90 percent of motocrossers - who dont jet their bike well anyways - this is is non issue, and I'm sure the FI system will work great.
I know a few individuals who have done FI systems to their street RZ's in various states of tunes. From what i gather, they have been fairly sucessful - but getting the perfect fuel map is REALLY hard and extremely time consuming. This is true of any FI project.
Making it all work seemless on a dirtbike will be tough without a battery system - but that's a simple hurdle.
o2 sensors are almost worthless on a two stroke...egt monitoring and a good tuner (person/human) is much more effective...