TOPIC:

As I noted already, I doubt your problems are due to the main jet but are attributable to the jet needle. Only focus on getting the one area fixed. By swapping main jets at the same time as modifying the jet needle position, you will only confuse the issue; especially since the main jets are allowing you to pull well at the top. Once you get the hesitation issue fixed, then tackle the main jets to see if they are actually a bit rich as I suspect.

What pilot jets are in the bike? The pilot jets affect mid-range just a smidgen and it might be possible to increase the pilot jet size a bit by some trickery and help solve the flat spot but first do some experimenting with the stock jet needles.

I am using the stock pilot jet. I did clean it very well upon removal. Here is a link to a pic of the carb specs out of my haynes manual. My bikes application is the zx550 a1 which is on the far right hand side. i21.photobucket.com/albums/b295/NoEardGoat/85gpzcarbspecs.jpg

I will not mess with the main jet as you advised. Let me know if you think I should change the pilot jet. I will try the stock needle today after work.

You should surely use a new set of larger pilot jets but unfortunately, there are none available that I know of. Unfortunately, Dynajet doesn't provide one... on other carb Stage 3 kits they sell, they usually put in an "air corrector" which I BELIEVE is an obstruction you place in the air jet that feeds the pilot circuit in order to effectively increase the fuel to air ratio. I have never been sure why they don't put a pilot jet in as tuning the pilot system is often difficult in a very lean situation caused by free flowing exhausts and aftermarket intake solutions... That is why I suggested mucking around with the stock jet needle before we investigate what can be done about the pilot jets... keep us up on how the stock jet needles work out and make sure you shim them if you still have a flat spot.

I did buy some carb rebuild kits from dennis kirk. I believe they came with some new pilot jets. Should I give this a try if the stock needle doesn't solve the problem?

I am also going to run the bike in the garage with the pods off after I feel the stuttering symptoms. That way I can see how the slides are moving.

took the bike out and warmed it up with the clip on the needle jet still in the 2nd positon from the top to cause the symptoms I am having to inspect the sliders. The bike ran crappier than ever and when it got warm it wouldn't move at all past 3000 rpm in any gear (lucky I stayed close to home), and actually died on me. I had to run it with the choke on.

When I got home I started it back up on the stands and with the choke on and checked out the sliders. They hardly moved at all. They moved 1-2cm at around 6000 rpm and a total of maybe 4cm total when brought up to 9000 rpm. They also shook a lot hitting the side wall in the carb housing. All of them acted the same and looked in sync with eachother

Should I now try the stock needle? I am not sure how much the sliders move and such so I will wait for advice before I proceed with the stock needles.

Try the stock jet needles. Not sure what else can be done at this point. As far as movement of the slides, that doesn't sound like they are moving sufficiently. Check engine compression. Then remove the slides and use fine steel wool to polish them and the carb area where they slide. Also CAREFULLY examine your slide diaphragms for holes/rips, etc. Blow compressed air through the opening where the slides vent with the slides out of the carbs...

took apart the carbs again, and cleaned up the sliders and their housing with some steel wool. It seemed to help a little and they slid a bit easier. No tears or rips in the diaphragms. Then I installed the stock needle. I then turned up the pilot screw another 1/2 turn so it was 4 turns out.

Well the bike ran well when cold, but still had the hesitation/stuttering in 5th and 6th gears when it got warm.

I have no idea which direction to head. Should I try the smaller main jet, even though it works great at open throttle?

Please let me know if you have any ideas. Right now I am clueless!!

I had a high speed sputtering on my cv34 keihin carbs that came on my kz750 H. I tried EVERYTHING from shiming the needles, drilling the main jets, rebuilt the carbs several times and could not find anything wrong with the diaphragms. carbs were very clean and seemed to be operating smoothly, however I could not stop the lean #3 cyl and the sputtering past 2/3 throttle. My solution after 2 months of jacking with it was to buy some mikuni VM28 mechanical carbs on ebay and have Wiredgeorge rebuild them. That fixed my problems and now I am back to riding again. My CV carbs didn't seem to be moving much either.