GSXR carbs

[RJ]

Got a set of '88-'89 series GSXR 750 carbs being shipped to me. They haven't arrived yet so I don't know what the jet situation is. Is anyone running these carbs on an 1100E (pods, pipe, DynaS, stock engine and cams) without a Dynojet kit? If so what jet sizes are you running? I'm cheap and don't want to shell out the bucks for a kit if I don't have to. Also any advice on cable setup or other install issues would be great.

 

[pano]

I have a set of 89 Gsxr 1100 carbs, Dyna jet kit and new K&N's that I plan to try out this spring/summer. If you can wait that long I will let you know.

 

[scotty]

are those the semi flat slides????

 

[pano]

I think RJ's and mine are supposed to be the slingshot carbs which I believe are the semi flatsides. Scotty I thought I read somewhere you had a set but hadn't put them on yet...but that was a while ago.

I picked them up because of what I read on this site. I want to see how they work.

 

[scotty]

I think RJ's and mine are supposed to be the slingshot carbs which I believe are the semi flatsides. Scotty I thought I read somewhere you had a set but hadn't put them on yet...but that was a while ago.

I picked them up because of what I read on this site. I want to see how they work.

yes i still have a set of 36mm semi flats from a 1996 750 Katana. They are spotless and still have the stock jetting in them. I got threm off ebay for just about $100 and sunk almost that amount into them for the parts i needed to modify them to a manual choke mounted on the left side of the carbs. i also modified an air box to go with them with a piece of very large pvc union cut and epoxied into it so i could run a huge K&N.
The idea is to have max air flow and not lose the dead air effect that the air box gives.
Now i wont use it because my gsxxxrrr 750 will get a set of real flatslides.

 

[Anonymous]

Scotty,
does that mean that your 36mm might be available, cause the more I dig into the carbs on my 1100E, the more possibly unfixable damage find (from previous owners/mechanics rough handling and gorrilla fist torque tactics). If so let me know.

Derrick "if I could just fix the idle circuit" C.

 

[scotty]

Duncan bone has first dibs but if you want them for $200 plus frieght ill sell them- i will include the modified air box and the rubbers from the carbs to the air box- The airbox is an 1100e air box.
I have 2 of them--one is stock and the other is modified. i also have a 1996 Kat 750 air box and a set of 1983 stock size 1100e carbs with 150 mains in them and shimmed needles to lean it out a bit
I think the stock size is 34mm. the kat carbs are large--

 

[Anonymous]

thanks Scotty,
let me know if Duncan passes on them, You wrote tthat you had set them up for a side choke, but how does it look as far a getting a throttle linkage to work?

Also when you say the Kat carbs are large.. not to large for my 83GS1100 stock motor with 4:1, and dyna coils?

Derrick

 

[scotty]

thanks Scotty,
let me know if Duncan passes on them, You wrote tthat you had set them up for a side choke, but how does it look as far a getting a throttle linkage to work?

Also when you say the Kat carbs are large.. not to large for my 83GS1100 stock motor with 4:1, and dyna coils?

Derrick

I just meant to say larger--36mm i think they were 2mm larger than the 1100 pots.
The carbs are up for grabs at any time. duncan will contact me if he still wants them

 

[scotty]

The connection for the throttle is in the front center just like on the 34mm stockers and it looks to be the same connection too.

I forgot to add this coment last time.

 

[Anonymous]

Hey Scotty,
I am so frustrated with my idle circuit on my stockers, I think that my intake leak is coming from wear in carb bodies themselves, specifically around the mixture screws where someone cut the bodies to get the screws out.
Lacento is near inverness right?, I am in Tampa and have the day off tomorrow (thursday), If you are willing, I will drive up and pick them up.
Saves me shipping cost and time, I realy want to ride my bike again.

Let me know, I will be on and of the forums most of the night.

Derrick

 

[Anonymous]

Picked up a set of 36mm Katana carbs today (thanks Scotty). and the look fantanstic (on my work bech at least, tommorrow they get installed)
I am starting with a 130 mikuni main, the mikuni 40 pilots from my stock carbs and I have shimmed the needles about 1.5 mm.
I will let you know how it goes as I tune.

By the way, I have a complete dynojet stage 1&3 kit for 16 valve 1100e's an 1150's for sale, only used for about two weeks and very little mileage.
$75.00 shipped in the US.

Derrick

 

[pano]

DerricC,

The following is a string of posts regarding the slingshot carbs on the GS bikes I dug out of the GSR resourses from doing some searches a while back. I cut and pasted so I would not have to search again. I did this months ago, there may be more. Keep us posted.

Beginning of what I found...

After having read many posts about the GSXR Slingshot carb mod for GSs, I obtained what I am pretty sure are some '92 Slingshot carbs for my '81 GS1100E. However, upon inspection, they appear to be downdraft carbs, with the bowls at about a 15 degree angle. Does anyone know if this will be problematic in terms of spilling fule into the cylinders, and does anyone have a solution? I would really appreciate some advice, before I wash out my cylinders and blow my engine. Thanks for any help.

Austin

I'm running the 90 GSXR 11's (36mm) on an 1150 with no problems now. I too was concerned about the angle. I had to lean the float height considerably to get it to run right. I bought my carbs used, and I think they may have been fiddled with previously.

The dyno jet kit that came with the carbs had these super blunt looking needles and huge mains. I fouled about 24 plugs, four at a time, until I leaned the floats.

In the meantime, I bought a Factory jet kit and the needles looked totally different, slim and pointy. I tryed these and fouled half the plugs mentioned above. My emulsion tubes, where the needle slides into, may have been fiddled with also so I stuck with the Dynojet kit. I'm using 32 pilots and 147.5 mains with the needle 4 notches down. I had it a 3 for a long while, but was experiencing detonation in the lower rev range. This change solved that..

I would reccomend a jet kit and K&N filters. If the idle adjustment screw is on the bottom it might need to be shortened, but if on the side with the long cable, no worries. The throttle cable needs to be shortened or a GSXR used. I modified my stock throttle housing to accept the GSXR cable, as it has a different end. Carter

Carter,

Do you have your carbs tilted somehow (like tied up to the frame) to level out the float bowls, or did you just leave them straight, with the float bowls at an angle? What height did you set the floats at, and are you sure that there's no raw fuel seepage into the cylinders? Have you ever checked the intake boots after riding to make sure that there's no fuel seepage? Are your plugs the right color? I want to use these carbs, but I'm nervous about cylinder washout. Any other information from you or anyone else would be extremely useful. Thanks to all.

Austin

Austin

I dont have them tilted, but I did fabricate a crude aluminum bracket to support the carbs to the frame. I mounted on the top of the inner carbs to the bar that supports the four carbs and connected to the two holes in the frame where the airbox used to mount.

The reason for the brackets is to support the weight without an airbox, but also maybe half a dozen times, I've started the bike and the negative back pressure or whatever its called, blew my carbs right off the boots. I also had three boots burst on startup.

Hopefully this is caused by the backpressure and not seepage.

My plugs tips almost look like they do when new, but inside the threads are darker. I actually think I'm running a little rich, but thats to cure the detonation on the 1229 with a little more compression than stock.

The floats are set at 17-18mm, almost as far as you can go. I had a shop do it as my hand dexterity is clumbsy.

When I've taken my carbs off, I noticed residual fuel on the ends of the boots, but I recall this with stock carbs too.

 

[Anonymous]

Thanks Pano,
I guess that I will modify my rear mounting bracket to elevate the carbs to level out the floats. I wonder how much angle my aging boots will take.
Thanks for the archive post, I will keep you posted.


Derrick

 

[Anonymous]

I guess it is going to have to be pods, I do not think that I can get the airbox to tolerate the angle, I may end up, at least initially, partiall restricting the pods though (tape ect) to ball park the jetting.


Does the down draft improve performance, even if the heads are not angled to match?

I wil know more tomorrow. Better try to get a lot price on plugs ,
Derrick

 

[RJ]

If you look on the "old Q&A" section under "performance" the first one or two entries is a piece about what great carbs the slingshots are when bolted up to the 1100. That got me going on these things but there's no specific info on jetting. I finally purchased a set. While looking for others with the same setup, I've come to find that guys are either running the BS34's, smoothbores, or RS's. Carter seems to be the only one who is actually running slingshots, and believe me I have dug all through this website for info. I guess it's going to be somewhat of a trial and error exercise.

 

[Anonymous]

Always is, I don't mind the experimentation, as long as I can make some progress.
I am looking forward to working with a set of reasonably pristine 8 yr old carbs (thanks again to Scotty) rather than a 23 yr old set that have been brutalized hacksaw modified. seems that shagged i( is this the correct syntax for this expletive?, maybe one of our GS kin across the pond will proof read for me, just ignore the typing, "Dammit Jim, I'm a Doctor (well ..in two more months), not a typist" ) idle mixture seats and threads were a big part of my idle problems.
Nyquil is making me punchy, time for sleep

Keep experimenting,
Derrick

 

[scotty]

i have the original katana air bo if you wnt to swap-I dont know if it will solve ur problm though. I hadn't gotten that far into the project

 

[RJ]

Well, you know if hot rodders from the 1950's could find a way to mate a flat head Ford to an Oldsmobile transmission, I think I can find a way to jet my carbs. I just would like to have a starting point close to where I need to be and not go through a million combinations of jets before I get there. Otherwise, long live the dinosaur GS and everyone have a good weekend.

 

[Anonymous]

After futzing around with my Semi-flatslide install I have a few observations to share.
1. After trying to cut my own boots, I jury rigged my torn boot with tape, andI have found that the stock 1100E intake boots can be used, it does take a little time to find the correct rotation to get the angle just where you want it. So I have ordered a new set of boots.

2. On the 96 Kat 750 carbs I am using, you can use your 1100E throttle cable, but it has longer action the the Kat, so you are near the end of the adjustment, also the cables exit angle is different, so you will have to reroute the cable to avoid binding. This is very important, because the return action on the Kat is much lighter than the 1100E, and will hang easily. I really like the carb mounted choke/enricher knob, it gets rid of some of the cable clutter on the bars and it has positive detents to keep it on when you want it on.

3. If you are going to try to match the downdraft angle, like I have (as opposed to adjusting the floats to compensate for the lack of angle) test fit your tank before you finalize any bracketry, the top of the far left carb will hit the fuel petcock with very little angle.

4. If you need to replace the fuel lines, you need thin walled line (Anybody know where I can find some?) because the OD of the correct ID fuel line from the auto parts store is too big, it will not fit between the carb bodies and if you route is outside, it is in the way for everything you do on the backside of the carbs.

5. there is a vacume port on the front right corner of the rightmost carb, that was not in my manual diagram, I used it for my fuel petcock vacuum. But it about drove me nuts looking for a vacuum leak. you can see it in the pic below

So after plugging my vacuum "leak" it starts, and even idles so-so. I still need to balance the carbs, and figure out the jetting.
I am thinking of eventually getting a dynojet kit for these carbs, maybe for the Kat 750, but I will see how it goes.

I will keep you informed

Derrick