Shim the needles?

KZ750 LTD...Keihin CV34 carbs.  I got my project bike running and rideable. Only one issue...it doesn't like to be held steady between 2--3K RPM.  If you accelerate it pulls right through the range and you never notice it.  The seat of my pants is telling me it's lean in that range.  Here's what I have done so far:  Carbs are clean, all jets cleaned out.  New manifold boots.  Ignition advance is free and working.  Valves are in adjustment (had to change one shim).  I'm running the factory airbox but the bike has a Mac 4-1 header.  All jets are stock except for the secondary main.  Stock is 125, mine has a 136 installed. I was thinking I'd get shims from Z1 and raise the needles...think that would help or should I change jets?...if so, which ones?  I really don't want to pull the carbs again until after the riding season.  Thanks in advance    ----bob

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To check if you are lean just feather the choke ( enrichener ) at the point of hesitation, if it improves then you are lean and some tweaking needs to be done which may be possible on the mixture screws.
You may als be a little rich on the mains for just the non stock exhaust and no other changes.

Shimming the needles has always worked for me in that situation. I have been able to do it without removing the carbs. Remove the gas tank. The top outside carbs are easy to get to. You may need an off set screw driver to get the tops off the inner carbs.

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Shimming the needles has always worked for me in that situation. I have been able to do it without removing the carbs. Remove the gas tank. The top outside carbs are easy to get to. You may need an off set screw driver to get the tops off the inner carbs.

I've had the tops off before with the carbs on the bike...that's why i was thinking of going that route first.  
 

I purchased a set of those washers over the phone several years ago, and returned them after checking their thickness for accuracy.
After spending ten-fifteen minutes with a digital micrometer at a local hardware store I was able to purchase several of matching thickness for the change I had in my pocket.

Well worth spending the time, IMO.

I like Zed1015 suggestion. You really need to know before you start playing with stuff. With the larger mains the transition area just off pilot to main through the needle taper might be making you rich before the air volume catches up. I’d be doing plug chops with repeatable runs and actually see what’s going on. You might open up a can of worms. What ever you do keep good records of your changes and only do one change at a time. It’s important to know where you started to understand the effects of the change. 

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.

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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?

I got new plugs when I was starting the project.  Here's what they looked like after my first 100 mile shakedown run...a bit of highway and the rest on the backroads

wrote:

wrote:

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.

Plugs look good. Maybe even just a tad rich. I can’t see for sure but it looks like you need to drop one heat range. B9eS. I noticed your have resistor plugs. Are you running resistor caps also. If you have resistor cap go to a non resistor plug B9eS. 

I'm not sure if the caps are resistor caps.  Would running both degrade the spark or harm the ignition?


Edit:  I did some cross-referencing and find my caps are resistor type.....5K