Do I have 76 carbs or hybrid carbs?

My 76 KZ900 I have owned since 1995 has carbs that have me scratching my head. I do not know if they are the original carbs.

They are 26 mm carb that were first used on the 76 model. However they could be off of a 77 or later. I do not know.

The carbs have the standard air screws on the air filter end of the carb and a pilot screw under the carb on the intake end of the carb.

The question, do I have a hybrid carb that should not have both screws.

The Clymer manual shows a break down of the carb and notes that some have a pilot screw and some an air screw model. Can a carb have both?

The problem is tuning both screws if you can imagine.

The carbs do fine other than the fact it will not idle under 1500 rpm. With 8 screws to adjust it is nearly impossible.

Wow I never seen them with 2 air mixture screws.
Must have been a Monday thing when they went back to work after 8 hours off. Must have been in the middle of re-tooling the machinery.
Sure would like to see a picture of this.

Some manual slide carbs have only a side-located pilot air screw.

Other manual slide carbs have only a bottom-located pilot "mixture" screw.

While not having seen one in the flesh, there are discussions about a third version of manual slide carb that has both a side-located pilot air screw AND a bottom-located pilot mixture screw.
And some of the kawasaki.com diagrams for other models show manual slide carbs with both type pilot screws.

Here's a pic of the Yeti carb with "pilot fuel screw" (actually a pilot "mixture" screw) AND a pilot air screw.

As I recall, the tuning suggestion for such carbs with both pilot adjustment screws is to first disable the bottom-located mixture screw by tightening it against its seat, and then proceed using only the side-located pilot air screw to fine tune the carb pilot circuit.

The last two pics show comparison of the two different manual slide carb pilot circuits.

Good Fortune!

Stock 1976 KZ900 has Mikumi 26mm manual slide carbs with side located pilot air adjustment screws.

Thanks Patton for the the info and the diagrams.

I will try closing off the bottom mixture screw and use the conventional air screw for idle mixture adjustment.

Always remember,if the screw is in front of the carb body it is a gas mixture screw. if it is behind the carb body it is a air mixture screw.

Look at the diagram on the right. The front screws are for the idle circuit. They should have very sharp adjusting needles and if you screw them in too tight they will break off and the circuit will be clogged.

I would suggest they be set at the factory setting and left alone for the time being. Roy

I have no advice to offer on the issue of multiple idle mixture screws but one observation if I may. On the issue of 1500 rpm idle. Are you basing your rpm off of the factory tach? My KZ1000 likes to idle at 1500 rpm according to the original tach, but my particular gauge is a bit "optimistic." As verified by a digital tachometer that is reading from the output on my electronic ignition 1500 rpm gauge = 1100 real. It is possible that your gauge does not read correctly, thus returning a false high rpm?

I have no doubt that having to adjust 8 screws to get your idle mixture correct would be a hassle that could lead to performance issues. It would be nice to have access to a wide band O₂ sensor in this case.

I tried closing off the mixture screws and ended up turning the air screws in to get an idle that was around 1.5k and still kind of rough. The air screws ended up being out only 3/4 of a turn.

The point that the tack is reading high is probably part of the issue that I had not considered.

My speedo reads 10 mph fast at 60 mph.

The mixture screws do have a sharp end and I see the potential of beaking and end off. They have orings that are old and brittle and that could be an issue.

According to the Clymer manual, the mixture screw carbs started in 77.
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There listing for carb adjustment gives the turn out for the air screw carbs 73 through 76 and the adjustment for the mixture screw carbs from 77 on.

None of the specific carbs do they give you a adjustment for air screw and mixture screw on the same carb, yet mine has both.

Thanks for the advice.

I'll toss in my .02c, I would try to set the Air Screws around 1 1/2 turns out, then see where the fuel screws make the Overall mixture Idle best.
It would be interesting to know how many turns the Air screws are at when the fuel screws are closed. I would think it wouldn't want to run well, Lean, with the Fuel Screws closed. Why there is a screw for each on your carbs, well it would be a guess but must be manufactured when the design was changing. Some engineer thought it would work with two adjustments. Bet he never saw a screw driver in his life, let alone a running set of carbs.

IIRC there were some Kz bikes that came with the carbs that have both a fuel and air adjustment screw. This is certainly a fact related to the kz650s, but they had the smaller vm24ss carbs.

I have read that all the Suziki bikes that came with vm26s had both types of adjuster screws. The pic that Patton posted is from a how to on the GS resource site. I am pretty sure that some of the larger KZs had them to.

At to settings I would set the fuel screw which are on the bottom of the carb turn these out 1 3/4 turns and leave them there. Then set the air screws which are on the side of the carb bodies about 1 3/8 turns from lightly seated. Then when you tune the pilot circut use the air screws only - the the fuel screws where you set them.

gd4now wrote: IIRC there were some Kz bikes that came with the carbs that have both a fuel and air adjustment screw. This is certainly a fact related to the kz650s, but they had the smaller vm24ss carbs.

I have read that all the Suziki bikes that came with vm26s had both types of adjuster screws. The pic that Patton posted is from a how to on the GS resource site. I am pretty sure that some of the larger KZs had them to.

At to settings I would set the fuel screw which are on the bottom of the carb turn these out 1 3/4 turns and leave them there. Then set the air screws which are on the side of the carb bodies about 1 3/8 turns from lightly seated. Then when you tune the pilot circut use the air screws only - the the fuel screws where you set them.

gd4now,
I took your advice and adjusted the air screws and the fuel screws as suggested and it started and idles better than I can remember in the past few years.

Thanks