Jet needle hardware question

Trying to sort a small problem with the set of VM26 carbs on my 78 KZ1000A2. The bike has a bog when you first roll on the throttle at idle. I have confirmed by use of a wideband O2 sensor that the mixture goes rich (10:1) when this happens. Unfortunately, this corresponds to the same throttle position for steady state cruise at 45mph in top gear where the bike stumbles noticably. I have the rest of the jetting right where I want it, and the bike runs really well otherwise.

So I was reviewing the parts diagram at kawasaki.com and discovered somethings that I seem to be missing. Looking at the attached diagram, I don't have parts #42, 43, or 45. I just want to verify their correct installation as I have no experience with these particular carbs other than the set that I have. If I'm reading the diagram correctly, the jet needle #17 is inserted through the washer #45 and the spring #43 and then the throttle valve #18 so that the circlip #16 rests on top of the washer. Then the ring #42 is on top of of the circlip. If this is correct, it would seem to explain why I have to use #125 main jets and needles on the 5th clip to run right. I also am running #17.5 pilots, and I suspect that if the needles were correctly positioned, then I could step down a pilot size and remove the rich condition just off idle.

Also, I have 5DL31 needles and the correct needles according to Kawasaki are 5CN7. According to my research, the 5DL31 needles are leaner at higher throttle settings than the 5CN7. Possibly supporting the need for very large main jets in a basically stock motor. OBTW I'm running the dreaded pods and 4 into 1 exhaust.

Edited to add picture.

testarossa wrote:

Trying to sort a small problem with the set of VM26 carbs on my 78 KZ1000A2. The bike has a bog when you first roll on the throttle at idle. I have confirmed by use of a wideband O2 sensor that the mixture goes rich (10:1) when this happens. Unfortunately, this corresponds to the same throttle position for steady state cruise at 45mph in top gear where the bike stumbles noticably. I have the rest of the jetting right where I want it, and the bike runs really well otherwise.

So I was reviewing the parts diagram at kawasaki.com and discovered somethings that I seem to be missing. Looking at the attached diagram, I don't have parts #42, 43, or 45. I just want to verify their correct installation as I have no experience with these particular carbs other than the set that I have. If I'm reading the diagram correctly, the jet needle #17 is inserted through the washer #45 and the spring #43 and then the throttle valve #18 so that the circlip #16 rests on top of the washer. Then the ring #42 is on top of of the circlip. If this is correct, it would seem to explain why I have to use #125 main jets and needles on the 5th clip to run right. I also am running #17.5 pilots, and I suspect that if the needles were correctly positioned, then I could step down a pilot size and remove the rich condition just off idle.

Also, I have 5DL31 needles and the correct needles according to Kawasaki are 5CN7. According to my research, the 5DL31 needles are leaner at higher throttle settings than the 5CN7. Possibly supporting the need for very large main jets in a basically stock motor. OBTW I'm running the dreaded pods and 4 into 1 exhaust.

Edited to add picture.

The washers would be plastic & the lower one is quite thick. Under that you would have a spring.

If those are missing, your needle would not be anywhere near the correct design position. You would be able to lift the needle with your fingers & rock it up and down a VERY noticeable amount. We're talking several mm, not thousandths of a mm...

As such, the needle would have nothing securing it firmly in the slide. It would drop to the bottom of it's mount well and on closing throttle, the friction of the needle in the needle jet could allow the needle to move up toward the throttle arm several mm.

If your carb rack is missing those parts and is designed to have them, you need them.

The last OEM USA model I recall using 5dl31 needles was the 1977 KZ1000 LTD.

Pop off a filter. Open your throttle. Grab the needle with some tiny needle nose or tweezers and see if you can move it up and down inside the slide... holler back

Larry C

As for oil consumption, I must say that I have noticed that the bike uses about 1/2 quart per tank of gas.

OK, I did as Larry suggested, and the needle isn't moving much at all. So that theory is out the window. As for the 5dl31 needles, it just fits with all the other LTD stuff that was hung on this bike when I bought it. It is an A2 frame but the bodywork, seat, and bars were LTD pieces, so it makes sense that the carbs would be from an LTD.

I'm not happy about the oil consumption, but it has seemed to diminish slightly as I go. I probably have about 500-600 miles since I got it running. Speedo isn't connected, so I'm just guessing about the total mileage. My plan is to put a 1075 kit in it with a ported head, cams, and probably something like those 29mm cr special carbs. I just got my spare head the other day, and I'm working on getting the funds for pistons as we speak. That GS750 is almost ready for sale, and if I can move it, I'll be well on the way to my plan.

I can live with a worn engine for a while. I guess I could do the dreaded compression test.

If they are from the LTD, the needle jet would be O-5, pilots 15, stock mains 105, 5DL31 needle.

If you came across a rack of 28 pumpers and put your needles in them, you'd have a pretty good set of stock carbs to work with... JMO

PS...throw a timing light on it and make sure your cylinder pars are firing 180 apart and the advancer isn't bouncing all around. Weak springs are common as well as binding from corrosion...