Gsxr Frankenstein project, need carb help! - GSXR.com
 
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post #1 of 7 (permalink) Old 01-10-2017, 04:07 PM Thread Starter
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Gsxr Frankenstein project, need carb help!

"Calling the Oldscool gsxr wizards"

Hi there, my names Julian and this is my first post, Woot woot! (If I can get this thread directed to the right area that would be awesome)

So I'll try to sum up a long story short. A buddy of mine built bike 1992 gsxr 600 with a 1994 750 motor. And now I'm building the same frame with a gsxr 1100 motor. This is besides my topic at hand, but I've been reading into this for about 4 months now. Others have done this in a distant land so it is the reason I'm doing it. Already have all the parts bought (motor, and a lot of other parts)

Total invested into this bike is approaching 3k which could of bought me a newer built bike... but wheres the fun in that? xD

So here's my question Im stuck on. I'm in the process of finishing up my conversion of the 750 carbs to work on the 1100 motor. I have a factory pro kit (mark at factory pro said I'm the first to buy the kit in 3 years) that's a stage 3 kit to convert "California" 750 carbs to an 1100 motor.

So here's my 2 options I'm left with at the moment;
1: I install the California 750 carbs the way I have them built at the moment and run the bottom purge lines to the bottom of the bike to drain or cap them because it's a vacuum line?
2: I just move all the parts to my gsxr 600 carbs I have, aka diaphragm and caps, all factory pro stage 3 jetting components, floats and bowls. Because it seems like these are the same between both carbs except the petcock vacuum line runs out the top diaphragms on the California with purge hoses on the bottom. And the non CA 600 carbs have a vacuum port on the side of one carb and no purge ports for emissions.

Any insight is appreciated, and if you have any questions comment below and I'll reply with specs needed!

Thanks!
-Julian
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post #2 of 7 (permalink) Old 01-10-2017, 04:08 PM Thread Starter
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600 carbs
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post #3 of 7 (permalink) Old 01-10-2017, 06:24 PM
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Hopefully you get some feedback, but I never run carbs from a smaller engine.

Carbs are designed for a certain amount of air flow, the air mixing jets in the rear bell of the carb reflect this, the emulsion tubes and needles reflect this, the fuel valve feed holes as well as the springs in the slides.
If you have 750 carbs that have a special kit to work with the 1100, by all means try that before installing 600 carbs.

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"Crazy people don't know they're crazy, but I know I am, so I must not be crazy"

Last edited by Racerxxxgsxr1000; 01-10-2017 at 06:28 PM.
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post #4 of 7 (permalink) Old 01-10-2017, 08:02 PM
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Well, I'd just cap the purge on the 750 carbs if the 1100 doesn't need them. It won't affect anything in the carburetor.


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post #5 of 7 (permalink) Old 01-10-2017, 11:51 PM Thread Starter
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Ok, I guess ill give it a try and post my results. I am 100% sure it'll start and run just fine, my only thing is that once its running I wont be able to tell weather its running to full potential or not (Tucson doesn't really have any dyno's to test at) and going as to how much I'm sinking in I don't know if I'm doing the right thing or not. the bike is old but I want to get it running like if it was new from its own year and at the same time have the ability to adjust the carbs if needed. I could of just bought 1100 carbs and thrown them on but if you guys have ever tried installing the stock air boxes on these bikes from these years you should understand why I'm trying to convert it to pods

Ill cap the purge hose and give it a shot. I guess I just didn't know what bad that might do instead of hooking it up to the canister its supposed to be in. I'm pretty sure I killed my last motor because of not installing one of the diaphragms properly on the carbs when I got the 750 and didn't know any better at the time. : damn:
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post #6 of 7 (permalink) Old 01-11-2017, 06:01 AM
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Well... Carbs are a finicky business because fuel delivery is finicky. I'm guessing it ran lean on the old motor?

Anyway, as far as performance, that's hard to say. Modern fuel delivery systems take in massive amounts of information and decide on how much fuel to give from that. Mass air flow, ambient temperature, air box temperature, ambient air pressure, throttle position, oil or coolant temperature, exhaust O2. Sometimes more. Carbs were built to a specific set of all those variables.

By putting a smaller carb on a bigger motor, that all changes. But how? Well... not sure anyone knows exactly. Some could probably make educated guesses, like that kit you got, but you'd still have to hit a dyno for optimal performance. Even then, it'd only be optimal for the exact air temperature, pressure, and relative humidity.

Carbs are like using a sledgehammer to drive a nail. You can do it, but if one thing changes from your calculations it all goes to hell.

I'm sure there's dynos in Tucson. Even in places like Houston you only find one or two with a web search. But the Harley service department I went in when I got a flat had a dyno even. If they install power commanders, they either have one or can point you to someplace that does. (And with 90's materials, 2.5-3 bhp per cubic inch is a decent rule of thumb for high performance engines. So 140-160)


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post #7 of 7 (permalink) Old 01-11-2017, 05:11 PM Thread Starter
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I'll look around town for a dyno again, your the first person to mention the Harley deal so here's hoping that might happen.

As for the whole "smaller carbs thing" that's what I was trying to say. I don't think that the makuni carbs bodies are different in size. The 600 and 750 carbs I have have different parts on it, but the same size bodies. And from what I read the 1100 uses the same size bodies too.

I think I will use the 750 carbs and see what happens because there is a different kit for the 750 to 1100 California carbs and the 49 state 750 to 1100 carbs. Based on what I gather the California kit might accommodate the vacuum leak that comes through the canister... so I might be running a microbial more rich plugging the purge ports right? Can't imagine it'd be too much, but for the sake of learning this does make sense right?
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