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Best to run non resistor plugs if possible.  NGK seems to be discontinuing non resistor plugs but there are still a lot of them out in the marketplace, and you can also run ND plugs too.

B8ES or W24ES or W24ESU

I tend to doubt using a resistor plug is causing the stumble being experienced but I'd change them anyway.

I found the B8ES plugs that were originally in the bike & they didn't look too bad...I put them back in for now.  If it's easier to find resistor plugs I'm thinking about getting non-resistor caps.  I was planning to build a new set of wires eventually anyways.

You must only run one source of resistance.
Running two will weaken the spark and can cause low speed running issues.

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You must only run one source of resistance.
Running two will weaken the spark and can cause low speed running issues.

This is what I thought until someone here pointed out that some KZ's, such as the later year KZ550's for Canada, came spec'ed from the factory with resistor plugs.  I think the bottom line is that if the ignition system is strong it can push plenty of power though the coils to fire resistor plugs.  This is not to say that resistor plugs are optimal though.  

Ok...back to shimming the needles.  I pulled the top off of one of the outer carbs....found an easy way to get the screw out that holds the needle in.  To my surprise I have needles with notches and a clip...I thought the needle was not adjustable.  Further..there were two shims in there ON TOP OF THE CLIP!!!, which does nothing to raise the needle.  Shims in or out the needle is free to move up and down a bit in the slide.  Not sure where to go from here....any opinions?  It wouldn't be too hard to put one shim under the clip and raise the needle a bit but I don't want to waste time and effort if it's not feasable.    .....and should there be a bit of up/down play in the needle when installed?

No need for shims if you can move the clip to adjust needle hight. You did not mention what notch the clip was in.
I would verify all carbs a set up the same. Ditch the shims and move the clips one notch.
 

Apparently these aren't even the correct needles for these carbs....it's a wonder it runs as good as it does.  Yes...I know i could have changed the clip position.  I'm real good at dropping and losing small parts.  The shims were sitting right there on the bench so i put one under each needle.  The needles that are in there have 6 notches...my clips were in the third from the bottom.  Looking at parts diagrams the CV34 should have a fixed position needle with no adjustability.  Also they're made from unobtanium as nobody has any.  Anyhoo adding one shim seemed to lessen the rough spot but not eliminate it completely.   Not sure what my next step will be besides ride it as-is.

Not sure if this is causing any issues as the bike seems to have a few mods going on.
I'll just throw this out there. 4 into 1 headers can cause a flat spot in your torque curve.

www.cycleworld.com/how-do-motorcycle-exhaust-pipes-work/


 

Ok....I found a set of four of the correct needles (N01A) from a supplier in the UK (NRP) for a bit over $60 shipped so I ordered them.  All this time I've been playing with myself trying to get it to run right with the wrong needles in the carbs....I wish I had checked that sooner.  

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How many turns open are the pilot screws?  And did you vacuum sync the carbs?

BTW, when you post with quote here be sure to click below the red line, that way your response will not be inside the previous quote area.





 

Yes I synched the carbs...got them just about spot-on. I forgot to mention that.   I started with the pilot screws out 2 1/2.  I took them out another turn and it seemed a little happier.  Think I should take them out a bit more?

3.5 turns open is pretty much the limit.  Opening more doesn't provide more fuel.
I've never messed around with shimming the needles but I have tried to remove the needles before and can say that the screws in the slide holding the needle is not easy to remove.  Be careful you don't strip out the slot in the screw                                 



 

I used a hollow ground bit from my Chapman gun screwdriver set...#98.  The ratchet handle helps greatly but I tried one with the regular screwdriver handle and was able to get it loose. The screwdriver set has mostly bits for slotted screws...the 2 small Phillips are not JIS.  You can get individual bits from Chapman for abut a buck-fitty each