MIKUNI 36s-HELP

[j31driver]

Okay, got 91 36 Mikuni's from a GSXR 1100. They have the stock jetting. Lowered the float height by 2mm to stop the flow over. What can be done about the pilots? It is just pig rich on the bottem end. I lowered the needles one grove. Once moving the bike is way better than stock. Any ideas?

[pano]

I picked up a set of these carbs but have not put them on yet. Here is a cluster of a bunch of posts on the subject that I previously cut an pasted when searching for info. It may not answer you specific question but worth reading.


.....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.

The power delivery is amazing, the pickup off the bottom, and the lightness of the twistgrip is addicting. Feels like a new engine.

One hot tip is to mount the cable to the carbs before installation, then route the cable through the frame. Try it the other way and you'll cussing and cursing. Carter

If you can get a copy of a book titled "Superbike Preperation" by Jewel Hendricks, it goes into detail on this subject and many others dealing with engine and suspension modifications. It was written in the mid 80's and it deals with these older bikes before fuel injection and shim-under bucket valve trains became the norm. My copy is full of greasy thumbprints, it is well worth the $20 or so bucks. Ride On, Ed.

I'm running GSXR carbs on my 83 Kat. It does have an 1150 motor in it but I dont' see a problem running them on the 1100 as I've tryed 36mm 1150 carbs on my 80 1100 with no problems except a rich idle circuit or improper float height.

I'm currently using 90 36mm GSXR 1100 carbs with stage 3 jet kit and dual K&N's. I think you'll run into problems trying to plumb them on a stock 1100 airbox setup.

I had to fiddle a bit with float height as I was told the GSXR carbs are sensitive to float height. I was told to start at 14mm float height but ended up fouling numerous plugs over and over until I set them at 17-18mm. Actually you may have better luck with a Factory jet kit and 14mm may work. I bought a Factory jet kit and tryed to install them in the carbs that had previously housed a Dyno Jet kit and I think the copper emulsion tube that surrounds the needle had been bored out before I bought them. That maybe why I was fouling plugs.

The throttle response was impressive and more immediate with lighter throttle action. The main jets were Dyno Jets equivalent to roughly a 160 Mikuni which seemed a bit big. I'm now running 145's.

Its a bit surgy around 2500-3000 rpms in 2nd and 3rd around town stuff and a delicate throttle hand is required at this low steady rpm. Otherwise its a vast improvement throughout the rpm range. Felt like a new motor was installed the first time I dialed them in right.

I did have to shorten the throttle cable, running a GSXR cable housed in the stock 1100-1150 throttle assembly. I also had the idle speed adjustment screw shortened as it was touching the cam chain tensioner.

I'm running a Pingel petcock with no vaccum line. You also must use a T- fitting to plumb the dual fuel line from the carbs. It's a go if you're into a little fiddling. I don't know anything about accelerator pumps. Carter Turk

[Carter Turk]

I just changed the needle jets in my 90 gixxer 11 carbs and discovered the #1 carbs needle jet was broken just below the main jet.

Turns out the PO drilled out the needle jet to fit the custom sized Dynojet needle . These needles dont even come close to fitting in the stock needle jet.

I tryed the Factory jet kit that is mentioned in the above post from Pano and things are working well.

I actually think I'm a little lean off idle, 2.5 turns out and pilots at stock 30. Mains are 142.5, needles are four down from the top and the floats leaned out. I can't tell you the exact number, but probably more than 17mm.

If you've somehow fitted these to your stock airbox I don't think you're getting enough air.

Bucking up for a jet kit and filters may be in order. I have an older set of dual K&N's if you have any interest.

I suppose you could try a 27.5 pilot.

[j31driver]

Does not look like there is anyway to make the airbox work. I have looked everywhere but 30 is the leanest pilot that I can find.

[Carter Turk]

How many turns out on the air fuel mixture.? I just turned mine out a half a turn to 2.75 on the way down to see Kevin Schwantz and the local bike shop and I think it made a difference.

What mains are you running and what the setup for airbox or pods?