Another KZ400 carb

This mess was purchased from ebay for parts. It's labeled 757A.

You can see the spacer is a little different from the 746C spacer.

Here you can see it's a little bigger than the spacer from the 746.

Throttle has only one hole and it's flat.

Has this bar that goes across the bottom and holds the throttle adjustment.

Jets were 757A stock size, which is 40 for the main air jet and 90 for the secondary air jet.

KZ400 vs TX500A carbs

Since I had a set of both all apart on my bench, I did a side-by-side. They are really similar. Some, but not all parts will interchange.

KZ400 will always be on top or to the left.

First we have the plates. As you can see by the choke spacing, the carbs are closer on the TX.

The KZ plate also goes deeper into the rubber holders.

It looks like the bowls are 100% identical.

Throttles physically fit, but the holes are in different places. Probably wouldn't run right.

Caps look identical. Gaskets look identical.

TX springs are longer. Might just be more worn...

Bodies look the same.

The bushing that goes into the choke area is different.

 Tops look the same.

KZ400:


TX500A:
60 next to the screw hole.
110 away from the screw hole.

Here you can see the brass restricting bushing difference.

 Same.

KZ

TX

KZ400 carb teardown (for real this time)

Ok we're going to try again. 746C is marked on the carbs. That makes them 1974. If we refer to the chart here, we see the standard jetting:

Here's an exploded view:

Another thing to be aware of is the butterfly screws are JIS. You can tell by the little dot on the heads. The best way to make sure you don't strip them is with a JIS screwdriver. Another option is to grind down the tip of a regular phillips.

Here you can see these guys. Top screw is 'vacuum plug' and it is removed when using factory carb synchronizers.
Bottom is 'pilot screw'. Before you remove it, screw in the pilot screw and note how many turns out it was. Factory starting point is 1.5 turns out, but it should be adjusted per the manual.

Here's the choke plug. Gods help you if it's stuck in there.

Primary and secondary air jets are 60/110. They were Keyster, so this carb has been rebuilt.

Standard jetting is 60 for the primary air jet and 100 for the secondary. The primary air jet goes into the hole closest to the screw hole.

These are called 'main air jet' and 'slow air jet' in the diagram above.

Needle jet with proper orientation. I use a chopstick to push them out.