Sputters at 0 to 1/8 throttle. Runs great from there up

78 Ltd 1000. Bike runs great under acceleration but is rough cruising with minimal throttle. Any ideas?
 

Welcome to KZRider Tim
Chances are your carbs need a good cleaning / rebuild.
Also there may be water in the float bowls from sitting 
Dave


Here is my 78 LTD

Carbs would be my first suspect, too. The pilot jet dominates the mixture at small throttle openings. It is tiny and feeds into several even smaller passageways into the carburetor throat. They can get clogged very easily by dried fuel or bits of debris. When clogged, they will cause the symptom you describe.

Also possible is that one or more of the choke plunger seals have become hard and are allowing fuel to pass even when closed.

Checking spark plugs after letting the engine idle at full temperature for a minute or two (without touching the throttle) may give you a clue as to which problem you have.

FYI--

to clarify, the spark plug evidence for dirty pilot circuit would be same as lean(white ceramic)? and the poor sealing choke would be same as rich(black/wet ceramic)?

Raising the slide needles may also help.

I cheated and installed a set of RS 34's on my 77' KZ 1000 LTD. Now it runs like a scalded dog.

Thank you, what a beautiful bike you have there. I’ll be taking things apart next week. Have a leaking rear master cylinder as well so I have a little work to do. This bike has been sitting for 10 years so I’m sure I’ll find many other problems. 

KeylAmi! wrote:

to clarify, the spark plug evidence for dirty pilot circuit would be same as lean(white ceramic)? and the poor sealing choke would be same as rich(black/wet ceramic)?

Yes. An infrared temperature gun might also be helpful, especially in identifying which cylinders are struggling. Since the bike has been sitting so long, the brake system needs to be completely rebuilt. The fluid will have a lot of water in it and all of the rubber bits will have deteriorated. Completely clean and rebuild both master cylinders and all the calipers. Replace the brake hoses, preferably with braided lines. Replace brake shoes if needed. I would replace them no matter how nice they look since the friction material is bonded to the backing plate and that bonding agent may deteriorate over time. Brakes should not be cheaped out.
Ten year old tires need to be tossed as well.
Next, I would carefully clean the entire fuel system and replace the rubber hoses there, too. Carefully inspect the carb holders. If they are really hard and showing surface cracks, replace them as they are likely leaking, or will be soon.
Finally, do all of the routine maintenance required by Kawasaki. 
When you are finished, you will have a reliable machine that operates as Kawasaki intended.

I want to thank everyone for their help. I’m trying to learn this as I go. I took the carbs apart and cleaned them using plenty of carb cleaner and an air hose, then put everything back together. Changed the jets to 120 main and 17.5 pilot fuel screw at 1 1/4 out. Bike ran great (maybe even a little stronger than before) under heavy throttle, however a little “boggy” on take off and at cruising. If I snap the throttle from idle it bogs, if I roll on the throttle it is fine. Came home and took the plugs out to see what I could. To me 1 and 4 look fine, but 2 might be a tad rich and 3 looks lean. Where did I go wrong lol. Before this all looked lean. 

wrote:

Changed the jets to 120 main and 17.5 pilot fuel screw at 1 1/4 out. Bike ran great (maybe even a little stronger than before) under heavy throttle, however a little “boggy” on take off and at cruising.


 

I am guessing pods and pipe (you never stated) What were the original jets?

I never recommend making multiples jet changes in one go because it makes it more difficult to diagnose what was wrong in the first place.

I suggest going back to your original jetting pre clean out as it just may have needed a spray out to clean the pilot circuit. Gas tarnish can build up rapidly especially if the bike has been sitting in unheated storage where temperature fluctuations can draw moisture (water)

If you have access to a Color Tune kit that is the best way to set the pilot circuit, especially for non stock jetting. You can also set by ear but its a little more difficult to master. Its either a pilot jet or air/fuel screw setting issue, it is not a needle height issue. If you still have black plugs afterwards it may be a choke plunger seal issue.
 

Yes, pods and Kerker W/baffle in place, sorry about that. Was 15 pilot and 115 main. All plugs seemed a little lean at that point. First cleaning the bike still sputtered at minimal throttle, so I took carbs off cleaned them again and changed jets. I am going to check into this color tune kit you speak of. Shouldn’t all the air/fuel screws be set exactly the same?

The airscrew settings will be different for each cylinder as they wear differently.
However, as the two cylinders which are sooted are 2&3 and they both run off the same coil a low voltage feed to that coil would cause your symptoms. Check the voltage at both coils are at the very least
11. 5 volts. If coil feeding cylinders 2&3 is less then resolve that first by cleaning all the connections, retesting, etc. Alternatively consider fitting the wired gearge mod which supplies full battery volts to the coils without the issues old wiring looms and switches can cause.