1983 KZ750 F1 Carbs driving me crazy!

Nessism wrote:

If you are in the US, I'll look them over for you.  I charge $250 for a rebuild, with all new O-rings.

If you want to continue on your own, you might want to make a leak test stand, with all the carbs ganged together, and using a remote tank.

And I don't remember mention of where they are leaking?  From the carb throat?  Are you filling the fuel via the center Tee?  Is the fuel tank free of rust?  Did you replace the needles?  

A video of the leaking would be useful.  

That is a great offer and very fair price. I may take you up on it. 

I have been testing them both off and on the bike. I have used the factory tank and a small (one quart) remote tank. Fuel is fresh and clean and so are both of the tanks. 
As far as the leaking, they will leak from the top of the clear tubes even if they are above to tops of the carbs. If I let them continue, they will start leaking from the bottom of the throat (filter side of carb) and then proceed to leak from the inlets including the oval type one at the top of the carb. It appears that the entire body of the 1+2 carbs are completely filling up. 

I am filling from the center T fitting when I have the rack assembled.  I have also rigged up a fitting to feed the individual carbs while apart. I will try and get a video or two and post them.

Paulkx5 wrote:

Wookie58 wrote:

Have you tried blowing with your mouth and a piece of pipe as they fill with the bowls on (it appears all the testing so far has been with the bowls off)

If I am following your question correctly, I have not done that. Are you saying to blow into the black plastic tee fitting vent?

No, once they are full, disconnect the fuel line and connect a hose to the fuel T on the carbs which you can then blow in gently (any that aren't seating will allow you to blow fuel out of the clear tubes used for checking float height) I don't know how else you could simulate "real world" with them on the bike

P1030291 by nessism , on Flickr

P1020761 by nessism , on Flickr

Again, if your carbs have the tube in the float bowl, make sure the brass isn't cracked.  I've rebuilt a LOT of these carbs, and most sets have at least one tube cracked, causing automatic overflowing.

 

Hi Ed, I have a spare set of VM24ss (kz650b1) that I am rebuilding and after reading this thread see that the brass tube you mention often cracks. This pipe on my carbs is mounted on the carb, can this be replaced? and are there replacement pipes available? I have one that is cracked around the small holes nearest where it is inserted into the carb.
Really interested to see the outcome of paulkx5 issues, as this will relate to a lot of owners.
Great advice regarding testing 👍
Rich.

OK, so this bike is the Kawasaki KZ750 LTD, correct?

kimchella wrote:

Hi Ed, I have a spare set of VM24ss (kz650b1) that I am rebuilding and after reading this thread see that the brass tube you mention often cracks. This pipe on my carbs is mounted on the carb, can this be replaced? and are there replacement pipes available? I have one that is cracked around the small holes nearest where it is inserted into the carb.
Really interested to see the outcome of paulkx5 issues, as this will relate to a lot of owners.
Great advice regarding testing 👍
Rich.

Clay pulls those choke pickup tubes out when cleaning the carbs, he's the guy to ask.  I haven't gone this deep-in yet.  I've replaced CV34 float bowl tubes, but never choke tubes.

I have a few replacement bowls for the 750 if needed? Keihins    are notorious for cracking of the bowl brass overflow tube as Ed mentioned! Kimchella, here's how i remove the casting choke tubes. I use a length of aluminum tube, slide over tube, twist and pull. Might note original height before pulling for future re-installation. I've trays of them and they differ from VM to VM. Clean, slide a steel pin thru, solder, redrill the holes along shaft and you're done. Little bit more to it but elementary. Make sure the solder doesn't corrupt the installation slightly tapered end or you'll have a time installing.     

Nessism wrote:

P1030291 by nessism , on Flickr

P1020761 by nessism , on Flickr

Again, if your carbs have the tube in the float bowl, make sure the brass isn't cracked.  I've rebuilt a LOT of these carbs, and most sets have at least one tube cracked, causing automatic overflowing.


 

Ed please educate me, I get that cracked tubes would cause leaks and premature "overflow" however how does it allow the carb to "over fill" (the OP said fuel was coming out of the clear tubes and the vents) I am confused how a "bowl leak" can cause the fuel level to rise above the floats ?

Wookie58 wrote:

Nessism wrote:

P1030291 by nessism , on Flickr

P1020761 by nessism , on Flickr

Again, if your carbs have the tube in the float bowl, make sure the brass isn't cracked.  I've rebuilt a LOT of these carbs, and most sets have at least one tube cracked, causing automatic overflowing.



 

Ed please educate me, I get that cracked tubes would cause leaks and premature "overflow" however how does it allow the carb to "over fill" (the OP said fuel was coming out of the clear tubes and the vents) I am confused how a "bowl leak" can cause the fuel level to rise above the floats ?

OP says the fuel is overflowing the "clear tubes", which I assume are attached to the float bowl drain nipple.  When the tube cracks, fuel runs into the drain, up the clear tube, and never stops.

To be honest, this is a long shot with the F carbs.  Kawasaki moved to eliminate the overflow tubes something about 1981 in the USA, but I'm not sure where the OP lives, and I've seen all kinds a wacky mismatched parts over the years.

Leaking thru the bottom of bowl, thru overflow barb can also be caused by plugged-up carb casting vents.

Hi Clay, here is a photo of the tube, the crack is around the gasket face height so will be tricky to pull out. I tried to send a PM but couldn’t? Anyway, can I buy a couple from you? I have sent you an email also 👍
Thanks, 
Rich

You can but try this first. Try pulling as outlined before. Have some tools beforehand though. You'll need either a 2.3mm (optimal) or 2.5mm tap, pitch will be 0.4 or 0.45. These will be needed if tube snaps off below the casting surface where the bleed holes are. All these VM tubes were 3mm OD and 2MM ID. Simply drilling them out can be detrimental if you use the wrong twistbit or drill off center. Pulling the remains out is a clear win-win. Tap remaining stuck tube bit, install a screw/nut/washer and collar and "pull" the portion out. Hopefully you won't have to do all this though! And FYI, the closed-end with the little hole in the center is generally .45-.5mm. A #76 is around .5mm, #77 is .43mm. Let me know how it goes?