Fastdruid

GSX-R600 throttle body on VFR750F (RC24) carb rubber. It is a perfect fit. No pissing about with different adaptors etc. Bodies split easily (with the loss of the secondary throttle valve) although its going to be a pain to forge the linkages. I know the RC36 carb rubbers have a different p/n and I don't know if the carbs are the same diameter there. (I'd have put it on the spare engine but its cold outside and the old rubbers are rock solid, I utterly failed to get it on out there)

Ah no, not personally and I'm not intended to. I mean in theory you could get something like 20% more torque on E85 (or potentially more, up to 40%) but you'd need to replace all the aluminium and rubber parts in the fuel system along with tuning to make the most of it.... E5 / E10 is likely to be more realistic which has issues already on older carb bikes with "carb jelly" not to mention eating unobtainium rubber carb parts (seals you can replace and some are available in E5/E10 proof but diaphragms etc are NLA) and then you have the rusting tanks... (although that is still a problem with EFI). I'm "just" planning on a big bore (837cc) + EFI which should see about 120hp (based on others who have done the same) running on "normal" pump fuel.

This is a technical discussion rather than a justification of if it is at all advisable! I'm largely in agreement...but EFI has a massive number of advantages over Carbs. It is more efficient, gives better starting, better emissions, it adjusts to altitude and pressure differences better. It is massively easier to tune and does not suffer as badly from wear or from alcohol (eg e85). But none of the more modern bikes are substantially better. 32 years after the introduction of the VFR750F and and the very latest VFR800 manages to be 10Kg heavier with the same amount of power and while I've not ridden the RC79 the VTEC of the RC46 was horrible and the engine uninteresting. Objectively it is a better bike in every way. Subjectively...it's a poor relation to the earlier models. I have zero desire for one and so the argument that it isn't worth it because there are new FI models is a poor one. I'm 98% in agreement if we're talking about stock bikes. Where it makes a difference is when you have modified it, the ability to tune with a laptop rather than spend a fortune on jets/needles and hours taking it apart and putting it back together again (and I *hate* taking the carbs on and putting them back on again). Still, even with modified bikes its more something to be done for it's own sake rather than because of any real advantage. So again I'm largely in agreement.

You don't need a cam sensor, you can have EFI without it but it limits you to wasted spark and either batch injection (ie random all cylinders squirt at once) or semi-sequential injection (one half squirt per cylinder every 360°, ie one squirt is correct, the other isn't) rather than fully sequential injection (ie one squirt per cylinder every 720°). Again note that the Microsquirt cannot do either semi or full sequential on the VFR750F or VFR800F (it could do semi-sequential on the VFR750R or RVF750R) as it does not have enough injector outputs.

Late to the party but I'm considering adding EFI to my project RC24 VFR (which is planned to be a 840cc '88 FJ engine in an '86 FG frame). I have the '86 FG engine but the '88 FJ engine is a better starting point with the *one* exception of the '86 having a cam sensor already (but smaller valves, different cams etc etc). '86 has a cam sensor *but* the crank sensor is useless for EFI. It is merely a single tooth trigger. '87+ RC24/RC36 has a 12-1 tooth wheel (11 teeth at 12 tooth spacing with one 'missing') but no cam sensor. '98+ RC46 (and the RC45) has a 12 tooth wheel & a cam sensor. The '86 runs non-wasted spark, all the others run wasted spark but single cylinder wasted spark (not sure about the RC46, it's probably non-wasted as the ECU knows where it is in the cycle). Any aftermarket ECU needs to have 4 separate IGN outputs. It doesn't look possible to fit a '86 cam sensor into later RC24 let alone an RC36 as the castings are different, it appears to be a small VR sensor slightly to the left of the front intake cam and picks up off a single "tab" off the cam gear. Although you could I think fit something in the same place and add a sensor in the cam cover. In comparison it is trivial to add the later 12-1 toothed wheel to the '86 and it looks like you should be able to fit the 12-tooth wheel to the RC24 and RC36. RC46 TB's are IMO more trouble than they're worth, the spacing is wrong, the angle is wrong and they're small. IMO you'd spend more time trying to adapt them than something else entirely. I'm not sure about the later RC36's etc but the 88/89 RC24 has 36mm carbs which are 44mm OD where they fit into the inlet rubbers. So I'm looking to use 2001-2 GSX-R600 TB's, these are only 2mm larger at 38mm ID and more importantly 44mm OD, ie the same as the original. They split apart and the plan is to sacrifice a set of old carbs for the linkages and top plate. Then use those to work them into the original airbox. Fuel rails will need to be custom, I have seen GSX-R1000K1/2 TB's which have a nice fuel rail that splits into multiple parts....but the TB's are too big and you'd need two sets to give enough "pieces" off the rails to work (and still need to fabricate additional lengths). I have one issue at the moment in that I'm not sure if Microsquirt is enough for the VFR. It only has two injector outputs and the 180° crank means even with a cam sensor you couldn't do sequential injection as the second cylinder would always be at the wrong point of the cycle so it would be batch-injection only. To do things properly would need duel Microsquirts or an MS3. Interesting about the multi-MAP though, I'll have to take a look at that.