My Custom GT750's

[Suzukidave]

My son Ryan tells me that once the engine is in the frame the rest of the wiring should go quickly so we will see , i will keep yall posted on progress

[tz375]

Dave,
How did you get on with those R1 throttle bodies?

I just got my hands on a set of 2002 bodies and they are the most complicated T/B's I have ever seen.

The radial flat slides are nice but a lot of flow disruptions

The 4 hole injectors are nicer than the GSXR set I have

They have an air/fuel mixture screw that I'm not so sure about

They have an interesting back bleed from one side of the butterfly to the other presumably to smooth down shifts.

They have a really odd system that looks like an enricher circuit but no apparent fuel supply.

No less than 8 vacuum bleeds, and 4 are plugged.

I'll have to strip them to see what's really going on, but I'd hate to try to set those up on a bike. I hope your 2001 set are simpler.

[tz375]

I took an hour off and stripped one of the throttle bodies. They are a very interesting design and I'm still not sure waht every aspect of teh design is there for or how it operates but I'm learning.

What I thought was an enricher does have plungers just like a BS40 or VM Mikuni but in this case they admit air through a bleed. What that circuit appears to do is to allow a graduated air bleed via a tapered screw which looks like a slow speed mixture screw. The hypothesis at this stage is that it allows a small and graduated amount of air to bleed from the airbox side of the throttle bodies to the engine side to improve off-idle throttle response..

The "choke" is activated by a solenoid and the hypothesis is that it allows more air in under strong deceleration. They sit in a cross drilling connecting the upstream and downstream sides of the butterfly valve.

The flat slides are also interesting. Air to the diaphragm lower face is admitted through two large, filtered, intakes mounted by the top caps. The diaphragm arrangement is similar to any CV carb and they have two holes in the base of the slide which allows the pressure above the diaphragm to equalize with the pressure in the throttle body bore. It's odd to see a slide with no needle after all these years of working with carbs.

I'll need to do some more digging to work out how and why that air bleed system works and how it could/should be converted for use on a GT750.

[Suzukidave]

Richard ... My son Ryan's thinking on the starter system is the air bleed to allow for a leaner " fast idle " so it lets in a bit of extra air .

[tz375]

He could be right. It's certainly a bleed from one side of the throttle plate to the other.

What makes it operate - vacuum or ? On mine the hose barbs are clean but naked, so I'm not sure what those two connect to. I did pull that servo/actuator/whatever apart and it's a really amazing design that hasn't revealed it's intent yet

[tz375]

Ryan is correct. The thing that operates it is the Plunger Control Unit and it's temperature sensitive so it uses radiator water to close the "choke" when the bike is warm enough. When the bike is cold the plunger is retracted and the "choke" plungers are out (on). As it warms up the plunger pushes the link plate to the left and allows the plungers to seat.

The air screws are a graduated bleed and they use that to synch the crabs after they have been mechanically synched. Screw them out for more air and higher vacuum across that cylinder.

Why they have so many vacuum hoses is still a mystery, but teh functionality is becoming clearer. At 40mm they appear to be really large but like all CV carbs with a butterfly valve, they don't flow as well as they might, so I guess they flow more like 36mm carb.

38mm GSXR600K1 uses secondary butterflies with their own servo for a sort of pseudo fly by wire, which are easy to remove and block off the shaft holes for a simpler set up and it's fast idle system is a manual cable which nudges the throttle slightly open. No air screw synch provision on the old GSXR either. It's simpler and much lighter which I like, but I'm warming up to the R1 system. It might take a little more work on the slides to get the throttle response right but I suspect it will e a more useable system for the street.

[Suzukidave]

There may be a better setup out there but i was just following the idea's of this guy http://www.smcomp.com/~smurph/RZ-EFI/index.html" onclick="window.open(this.href);return false; but he used the R6 throttle bodies on the RZ350 . I am hoping the CV type R1 TB's smooth out the massive power i will be getting out of my engine ( some day )

[tz375]

I remember that article well. Do you know what his results were? I thought there was a thread somewhere where he talked about the changes he had to make the mapping and the results he achieved but I can't find it now.

Did he use the wide band O2 sensor for example? So many people seem to try to use one and on a two stroke their life expectancy seems to be measured in months rather than years and unless we plan on touring at a small throttle opening steady state, there's not much need for one.

But I can't remember what his experience was.

[Suzukidave]

In the " sensors" section he shows the wide band O2 sensor he used . I remember Bill saying that he uses the heated wide band O2 sensors and gets good life out of them . Ryan's thinking is we will use mine mostly for the dialing in process and then pull it and plug the bungs . The bike will still have the full range of other sensors tho .. TPS , map , rpm ,water and intake air temp

[Ugly]

Whoa! Inspiring.

[cruisingram]

I am following your EFI with great interest. How does the EFI work with the mixed fuel- or where does the fuel get mixed- before the TBs or after? If I do no other mod to my motor- EFI is the one I want done.

[Suzukidave]

Hold on till we get mine running before you invest the time a money into this idea as some have a feeling this will not work out .

[cruisingram]

Oh yeah, let someone else do the dirty work LOL- I am really curious as well. thread is subscribed!

[tz375]

I am following your EFI with great interest. How does the EFI work with the mixed fuel- or where does the fuel get mixed- before the TBs or after? If I do no other mod to my motor- EFI is the one I want done.

Are you asking where the Injectors are placed relative to the throttle plate or where the oil adds to the incoming fuel supply?

I can't speak for Dave, but I'm planning on using a stock type oil injection setup and the injectors are downstream from the plates.

[cruisingram]

Thanks- that is really confusing me- me not being a two stroke guy, and not knowing how the oil is being mixed prior or after the throttle bodies. Or how the correct mixture is determined in oil injection.