Float Height Detective

Prepping a used set of carbs for my KZ750/4, and some strange issues.
1. Carbs 1&2 float levels more or less OK, only a few mm out
2. Carbs 3&4, big problems. At first, no flow at all
3. Carb clean and brushing on 3&4, still no flow
4. Bowls from 3&4 removed and cleaned, now they flow when off the carbs
5. When bowls removed from carbs 3&4, carbs show flow of fuel
6. Bowls replaced on 3&4, and no flow still
7. After tapping and blowing with carb cleaner, carbs 3&4 eke out some flow. But the levels are 14 and 20mm below top of bowl. This seems like too much to adjust for - am I right?
8. Taking carbs to shop tomorrow to clean AGAIN and test flow
9. It’s not plugged float valves, because I pulled those out (with an M6 tap), checked for blockage, and tapped back in
10. Its not float valve operation, checked that and it appears functional

Any advice on what I’m missing? Any advice on what to check next? Thanks in advance
 

Floats updide down ?
 

"Only a few mm out" is waaayy too much.  Carbs should be plus or minus 0.5 mm.

What carbs are you working with?  

If you have a problem getting flow into the carbs it's a simple process to track the flow from the fuel source forward into the carbs.  I would suspect plugged Tees or hoses.

Will check, thx

Kubik wrote:

9. It’s not plugged float valves, because I pulled those out (with an M6 tap), checked for blockage, and tapped back in


 

What does this mean?  M6 tap?  "...tapped back in"??

It seems clear that you need to perform a full carb rebuild, or find someone competent to do it for you.  The factory manual has lots of good info regarding the carbs... www.kzrider.com/service-manuals

Will check, but as I said, there is already visible flow when bowls off.

Saw that technique on YouTube. You literally screw an M6 tap into the float valve seat, turn the tap, and it eventually pops right out. Works well.
After cleaning and checking for obstructions (there were none) set the float seat back on top of the carb body and tapped it back into place. Checked float valve operation, and it seems fine.
Before doing this on my carbs, tested on some old scrap carbs to make sure it worked.
 

JR wrote:

Floats updide down ?

 

Saw that once on a Honda thumper.  Fuel level was so far off it was pretty obvious.  Looking closely for a polished wear spot at the float tab where it contacts the needle valve plunger, it might be very apparent which side was originally up from the factory.

Good Ridin'
slmjim & Z1BEBE

Carb type is a rack of four CK34 Keihins. My old rack had a really stuck diaphragm slide valve, so replaced with this used set.

Took all jetting out of the old carbs and put that into the replacement set.

No experience here with these carbs but if you screw a tap into a float seat I’d say it’s trash. Wouldn’t you damage the tapered seat?

Mikaw wrote:

No experience here with these carbs but if you screw a tap into a float seat I’d say it’s trash. Wouldn’t you damage the tapered seat?

Not sure if you would go in far enough to hit the taper, however the bore the valve runs in won't be very smooth !! maybe this technique is meant for removal only with a view to fitting new seats afterwards ??

The float valve seat is not removable on the Keihin CV34 carbs. What am I missing?

Edit: oh wait, did you say CK34?  Carbs from a later model 750?

If you ran a tap into the float seat, it's junk now.  Time to buy a set of float valves.