starts idles fine can't rev over 3500

I am confident this problem is carb related since I put my 82 1000 carbs on this bike and it ran fine.
1983 KZ1100 LTD BS34 CV carbs are giving me fits. I have completely disassembled and thoroughly cleaned them. The were never that dirty or gunked up (even though this bike sat at least 6-7 years).

It will start easy and run fine at an idle. Normal fast idle while on choke. Normal stepping down of choke after a couple minutes and it still idles fine. But it will not rev up past 3500 or so and is sputtering and blubbering at that. It won't rev at all until it warms up.

The 1 thing I noticed when taking them apart is that the diaphragms were not keyed right. PO had also taken apart the carbs. The vacuum hole in the slide is supposed to be on the engine side of the carb throat. I noticed no change after fixing that. The diaphragms are in excellent condition. Another observation is that the tube (the brass thing that is keyed and removed up through the throat after removing slide/needle) the mains screw into would just fall out (into throat) after removing main jet. I thought normally you have to tap them out with a wooden dowel.

The carb holders are a little cracked near the center, but spraying brake clean on them while running made no diff, and as I said it runs fine with the KZ1000 carbs.

I set dry float level, but have not done clear tube test as the bowel drain screws are not coming loose, and are on the verge of having striped heads trying.

I know this is a weird problem, but doesn't somebody have any ideas?
Need more info? Pics?

Try putting a small wrap of tape around your air filter, if it revs good then, you'll know its a lean issue, if it gets worse, its too rich for some reason. Also in the rear/inside of the carb there are air jets or airjet passages , make sure they are not plugged up. These air jets provide the air to mix with your pilot jet and main jets. The pilot air jet will be the bigger air jet and the bigger air jet will be mixing with the pilot jet. If you take out your main and pilot jets and blow contact cleaner through them, you should see some cleaner coming out the air jet passages in the rear bell of the carb. You can also spray through the air jet passages and see it come out your fuel jets. Just a thought that could be the issue.
Usually if your air jets are plugged with old dried gas (varnish) it will give that particular circuit a very rick mixture ei. no air mixing.

Thanks for that input on cleaning the air jets. I have done that spraying carb cleaner both ways and it seems to flow thru fine. The main and pilot jet air fuel passages seem to be clear judging by the flow of cleaner thru them. I read a tip about holding your finger over those air vents to check them too. Not very easy to do on 4 carbs at once.

Was there a reason you pulled off the 1000 carbs?
At home, I just used to buy the gallon of Berryman's carb acid from the auto parts store and disassymble carbs and soak them over night(removing all rubber parts first), then flush them with water and blow them dry with air and blow out all passages. That really is the proper way to clean carbs.
The poke and spray method can never be as good.

Since my 1000 was running OK, just as a quick experiment I swapped them to the 1100 to see if I had other issues causing the no rev problem. Since the 1100 was bought only hearing it run for a minute and riding a couple hundred feet with a stuck clutch I wanted to get a better idea if I was going to have to get way deep in restoring it to rideable condition.
I do have a gallon can of carb cleaner dip, but it's near 15+ yrs old (not really dirty from lots of use) I don't know that matters as far as effectiveness. I was hoping to avoid a complete disassembly of the 4 carbs to soak them 1 or 2 at a time.

ok, I understand now. Sounds like your lowspeed/pilot curcuit is fine, I'de suspect the main circuit or maybe a needle issue. Also make sure the needles dont move up and down in the slide, only the slide should move up and down with the needle fixed in it. I cant remember what kind of retaining plate is inside the slide to hold the needles..

The BS34 Carbs had different Needles/ Jet for the mid range. If your 1 set works, compare the jets, or swap the jets. Also look close at the slides, and compare the vacuum port size. Then of course these had filters above the Float Valve, make sure they are clean, don't want starvation playing in.

This is UK specs but you get the Idea.


Stock UK Spec. Mikuni 34mm carburettors as fitted to the following Kawasaki (UK) models.
Read L-R like this:
Model, Cross Pilot & Plug(Yes or No), Main Jet, Pilot Jet, Jet Needle, Needle Jet, Main Air Jet, Pilot Air Jet
GPz750R1, Yes, 110, 37.5, 4BE3, Y9, 250, 300
Z750L3,4, Yes, 110, 37.5, 4BE3, Y9, 250, 300
GPz750A, No, 110, 37.5, 4BC7, Y8, 250, 300
Z1000K1,2, Yes, 122.5, 37.5, 5FL52, Y1, 85, 350
Z1000J1,2, Yes, 127.5, 37.5, 5FLZ50, Y6, 85, 350
Z1000J3, No, 117.5, 37.5, 5CF58, Y2, 85, 350
Z1000R2, No, 127.5, 37.5, 5C48, Y4, 85, 350
Z1100A1,2, Yes, 120, 37.5, 5GX29, Y1, 85, 350
Z1100A3, No, 117.5, 37.5, 5CF58, Y2, 85, 350
Z1100R1, No, 130/5, 37.5, 5B5, Y8, 85, 350
Note: Numerical difference in main AIR jet size between the 750 and 1000/1100 carbs is huge whereas the difference in pilot AIR jets is much less.
Note: All the different main jet, needle and needle jet combinations.
Note: All have 37.5 Pilot Jets.
Note: Z1100R1 cylinders 1&4 - 130, 2&3 - 135 - presumably an extra cooling consideration for the two inner cylinders?
Note: All UK needles are 5 position adjustable (stock is No. 3 (middle) clip position)

This 1100 is totally stock. However the exhaust is pretty rotted and leaky near the crossover pipe, and I have the air box boots off during this trial run.
The slides, needles and all jets are stock. That will obviously affect performance with the likely addition of a header, but it should not drastically affect current basic stationary running i.e. no ability to get rpm's over 3500 even for a split second.
I have inspected diaphragms closely and see no defects. Slide vac holes are clean and uniform in size Previously not oriented correctly but corrected position changed nothing. The stock slide needle does have a slight barely noticeable taper. Using a mirror I observed slides raise slightly while opening throttle.
While dry float levels are correct, I have finally gotten the drain screws out and am going to use clear tube to check float levels. Since no overflow has been seen ever, low level seems more likely.

It won't want to run, without the AirBox Boots connected. Try the engine with it all hooked up correctly.

You need the air box boots. I've seen some stock bikes that wouldnt rev properly stock with no airbox or with no boots.
Also make sure your carb vents(vents for floatbowls in main carb body) are not restricted, hose folded or capped off)

The '83 1100 carbs with 117.5 stock mains have vent tubes on common rail line between carbs, 2 lines, which are new and clear. The '82 1000 carbs with 122.5 stock mains have the vents in the top of the inlet. Both are Mikuni's.
The bike really doesn't run any different from when I started working on it with the air box connected and before I double cleaned and checked carbs.
So doesn't it have to be the 1100 carbs if it runs OK with the carbs off the 1000 not connected to air box? The 1000 runs OK with UNI dual throat foam pods.

I'm really ready to pull my hair out on this one. I have rebuilt in the neighborhood of 100+ car carbs from 1950's models to 1980's computer controlled ones, and more than that from other motorized things over the past 39 years sine my first one. Bikes to mowers etc, 2 stroke ,4 stroke. I've never had the trouble I've had with these Mikuni CV BS34's