midget,
Something in the 38mm/40mm blade diameter should be adequate and give good throttle response. That should also allow sufficient taper in the inlet tract for a reasonable "energy gain" in gas speed in the inlet tract. I'm thinking shorter throttle bodies may give more manifold design flexibility. Try not to "re-invent the wheel" please.
You see, this is how Mark slows me up when I start trying to get creative.
He asks the question he KNOWS I don't know the answer to, and knows I won't be able to come up with an answer until next weekend.
Relax, I haven't dropped a dime on it yet.
Still the grasshopper in Beerhaven . . ., but I DO want to balance parts availability and serviceability into the equation. If you think about how difficult even Weber carb parts are to get ahold of these days, it sure would be sweet to be able to get replacement injectors and parts from Don and Roy's Cycle in Brookfield, rather than waking up at Oh-God:30 in the morning to call the Midlands and speak to foreigners in their own tongue and STILL miscommunicate what we're trying to do.
Jenvey makes a kit that bolts up directly to the head, but it's intended for 200 + hp 2 liter applications, and while I like the idea of a kit, our combination is just so weird that I question if much "off-of-the-shelf" stuff is going to be "the right combination".
I did come across a set of Yamy FJR1300 throttle bodies with injectors, which had about a 38mm bore and an intake diameter of 42 mm.
These aren't the actual pieces - but this is what I was looking at over at Milwaukee Cycle Salvage, and they included the injectors . . .
http://www.ebay.com/itm/05-YAMAHA-FJR1300-FJR-1300-ABS-THROTTLE-BODY-BODIES-B32-/350671137896?hash=item51a5a0ec68&vxp=mtrRex, regarding your offer, here's what's key - the throttle bodies must be individual pieces, not cast in pairs. Most of what I perused Saturday were cast as pairs. With individual throttle bodies, I can fabricate both a fuel rail and brackets, and come up with some sort of linkage. We're at 88 mm on center - most of the bike stuff I looked at was ~77. Mark wants a straight tract to the port - I think that makes more sense than goosenecking it like a Weber.
The FJR produces 145 hp in stock form at 8500 rpm - if the flow is correct for our app, I'm thinking these - or something similar - might be an option.
I also came across this - a set-up made for a Vauxhall C20XE out of a set of GSXR throttle bodies - it looks doable . . . and this wheel has already been invented!

Regardless of how we go, it's all going to need sorting, but I do like the idea of being able to optimize the intake track (tract? . . .

).