Keihin CV34 observations

I installed a lambda bung in header #2 so I can jet with confirmation. I have three disassembled CV34 sets which are different configurations so I had some question as to which parts go with which.

Just a few Saturday notes..

1) Turning the pilot screw in makes it leaner, out makes it richer. I had doubt since the screw is located at the top and in some cases this means air screw, but on the CV34 it is indeed a fuel screw.

2) There are at least two slide spring types, with about 1/2" different overall length. My 1983 KZ750 F1 LTD SHAFT likes the shorter springs. You can tell the difference if you look at the ends (see attached photo).

3) Some of the CV34 carbs have different heights in the slide area, such that some carb slides do not bottom out on all carb models. Strange. I chose a carb where the slide would bottom out properly.

My current jetting (stock 1983 KZ750 F1 LTD SHAFT):

jet needle: N01A
main jet primary: #65 (stock was #62)
main jet secondary: #125
pilot jet: #35
pilot fuel screw 3 turns out

Runs OK. Not spot on, but nothing dangerously out of whack. It's got a nice economy mixture for cruising and still hits about 13:1 when you punch it. I may bump the primary again to note the effect.

nice notations, keep them coming.

It's really confusing because as mentioned on this site there are two major CV34 configurations: one with dual main jets (and the pilot jet cap), and one with a single main jet. However, I have two of the dual main jet variety and they are also different from one another (different pressed hole sizes and slide channel height).

There are also a multitude of float styles. I chose the half-style floats which have a flat bottom because they are roughly parallel to get the proper fuel height.

The needle differences are crazy. N01A versus N10A are like opposites. N01A with a huge taper almost going down to a needle point, versus the N10A fat & blunt.

Overall the most confusing is that some slides will not bottom out properly in some carbs. In the diaphragm area, the rim which the slide rests on is different heights! Such that when you drop the slide in it sits almost 1/8" from fully seated in the venturi. This exposes the base diameter of the needle at rest. I don't know, perhaps that is proper versus the setup I used where the needle sits all the way to the hilt.

Oh I forgot, I also have two different needle jets. Different hole patterns. I'll have to add them up to see which goes with which carb LOL.

Hmm I just swapped from one style to another, and that is a subtle difference. Too small for me to notice seat of the pants, which is surprising because they have completely different hole positions and counts.

Wow the primary main change is huge. I went from #65 to #68 and the cruising 3k-4k is richer. Pretty neat trick!

I'm satisfied with the running except for maybe a wish for a bit more idle torque. This bike doesn't seem to tractor at 1500 rpm super well. I have to give it a little gas from a stop. It's probably an issue other than jetting though. Could also be one or more of the other carbs being wacky since I am only reading #2 with the gauge.

If I get a higher quality manometer I will try to do the idle drop procedure and get each cylinder's idle mixture set to its strongest.

One of the things I like about CV carbs is that they give you a nice temporary bump in fuel when you hammer them. You don't get a hit like a flat-slide with a/p, but you do get a nice acceleration surge. Though it kinda depends a bit on the damping rate of the slide.

Just a metric about the primary main on the CV34. So I ran with #68 for a while and then back to #65. During my 30 mile commute, which is freeway 55-65 mph it resulted in 38 mpg (#68) and 43 mpg (#65).

Sorry I never posted again in your thread.
Maybe this might help you if you don't already know.
There are two different CV carbs used on the Kaw's. Mikuni BS series, and Keihen.
The Keihen has the two Main jets, one slow main and one high speed. The Mikuni has the single main and the metal pilot jet plug. Jet sizes/ numbers are completely different as they use a different numbering system. They do not have interchangeable parts.
If you go to Kawasaki.com and then owner Info. You can pick a model with the mikuni BS34 series, 82 KZ1000 K2 will work. Then try a few 650 or 750 models from the early 80's to get a Keihen. They'll have the exploded views and part #'s.

Thanks for the note on which bike comes with the BS34. I just picked up a set to replace the CV34s on my kz750. Knowing where to find the part diagram will be useful when I am cleaning up the BS34s.

thread may be dead but Im curious

I was looking to see what kind of carbs where on my 83 KZ750 F1, and mine say keihin on the side, but do in fact only have a single main and one pilot jet. I thought for sure that mine would have the secondary, there is a slot for one (no outlet) but all three sets of my carbs are the same. so did i get jipped by Keihin or did they in fact only have the single main jet???

Apologies for not checking on this thread earlier. There were two, at least, different Keihin CV34 carb designs. I have them both, but prefer the dual main version because the primary main can be used to adjust the 1/4 throttle area.

I never did get the jetting proper for the single main style, as I have limited pieces. I do know that the jetting (particular jet #'s and needle #) is not compatible between the two styles.