'78 KZ650B - fuel dripping out of overflow tubes

Hi all,

I just posted a short intro on the noob forum...obviously I'm new here and to the KZ world, but not new to motorcycles. I just picked up a '78 KZ650B as a project bike to keep idle hands busy over the winter. It has been sitting since '95 but looks like it was actually "stored" properly for most of the time. The inside of the tank is clean, the carbs were not that dirty/ gummed up. A few hours of cleaning, lubing and a new battery and it fired up.... I do not profess to be a carb expert - so here is my issue. I cleaned the pilots, MJ and removed the air/fuel mixture screw to shoot carb cleaner through all the passages (I read a post here on this...) I made a couple attempts at setting the floats (dry at 23mm) but have not tried the clear tube test yet.

If I have gas dripping from the overflow tube (on 2 carbs) can it be any other issue other than float height/ fuel service level or a bad float valve?

Any help/ advise is much appreciated.

Thanks!

Probably just dirty float valves. You can clean them without removing the carbs. However, I wouldn't be surprised if you have messed up the float level. It may be too late for you at this point, but no adjustment to the float height should be done unless the clear tube test shows a float height problem. The float height never changes unless someone gets in there an starts bending things. So first clean the float valves on the 2 leaky carbs - use a Q-tip with some carb cleaner; don't use anything abrasive. After that, use the clear tube method to make sure the float heights are still ok. If none of the above stops the leaks you may have a cracked overflow tube in the carb bowl. This is easy to check without removing the carbs. Ed

Here ya go... pretty much everything you need to know about carb/rebuilding....

kzrider.com/index.php?option=com_docman&...d&gid=461&Itemid=108

OMR

It is possible to have the floats properly adjusted and still have a leak. I had a cracked overflow tube on my #2 carb which lead to a slow drip from that overflow. It was a very fine crack that was not discovered when I cleaned my carbs. Please do yourself a favor, and rectify the problem before you ride the bike. We recently had a member whose bike caught on fire, so don't take unnecessary chances.

Edit: Do the clear tube test before you disassemble anything again. That test will be the only way to really get the floats correct.

Thanks for all the help guys. Much appreciated.

I'll do the clear tube test next and see how things look.

I haven't ridden the bike and don't plan to put it on the road anytime soon - it needs a bit more TLC. Not only is the leaking gas a fire hazard, it is making my garage stink like gas to boot! (I have the tank off now)

I want to get the carbs sorted out before I move on to other things.

I did the clear tube test and things checked out OK. I pulled the carbs and bowls off again and found that the overflow tubes were cracked on both leaking bowls...

Now to find overflow tubes... Does Sudco sell that sort of thing?

I have recently found several sets of carbs with the vent standpipe cracked.

Here is what I did...

Remove the broken tube from the float bowl, after measuring the exposed tube length. (I use the rod end of a dial caliper) If the tube breaks off in the bowl, remove the remaining piece with a #2 easyout held in vice-grip pliers. Twist and pull...
Get a piece of 1/8" brass tubing, I got mine from a local R/C airplane and car hobby shop.
Cut the tube about 3/8" longer than your first measurement with a small tube cutter. This should reduce the diameter in the end of the tube and prevent splash over. Plus it looks nice too.
Take a scribe and firmly hold the tube, gently roll the scribe in the end of the tube in the un-cut end to give it a slight flare. Sand this flare smooth, should have a slight bulge. Tap the tube into the float bowl with a piece of hardwood or plastic (like a screwdriver handle), with the recently flared end in. Make sure not to drive the tube in too far or you will have to remove it and make another. Set the open end height to the measurement you made at the start.
Leak check the vent by holding the bowl in a vice or something stable and fill with fuel or alchol to the top of the float bowl. If you still have a leak put a small bead of JB Weld around the mating area and allow to dry 24 hrs before putting fuel on it.
I will try to get some pics and post them later.

BTW the clear float tube check is BS, only good to ensure the carb is not overflowing from float height, no good for setting the float height. (Make sure the float height is ok? what is the "clear tube" spec?) Myth!!! The only right way to set float height is by using the factory measurement to get the jets in the correct depth of fuel. Dial calipers work very well for this,be sure to measure the float at the highest point if they are round brass, or in the middle of the "average" height of the float if composite. I have seen 2 sets of carbs this week that were set at the heel next to the float pin, which makes the fuel level almost 2mm too high.
Also most importantly, make sure the floats are parallel to each other when floating on their pivot, lots of times they get "tweaked" during cleaning.

sbruton wrote:

I did the clear tube test and things checked out OK. I pulled the carbs and bowls off again and found that the overflow tubes were cracked on both leaking bowls...

Now to find overflow tubes... Does Sudco sell that sort of thing?

I cleaned my bowl out real well to remove any traces of fuel, and then soldered the cracked tube. It's holding for now, but I plan on getting a new float bowl when I can find one.

Just out of curiosity, did you have your carbs ultrasonic cleaned?

FYI, the clear tube spec is 3mm below the flange on the carburetor. I respectfully disagree with wargoth's assesment of the clear tube test. If it didn't work, then how does a water level work? I believe that the clear tube provides the most accurate measurement since it demonstates actual fuel level. Setting float heights with dial calipers assumes that all floats are perfect with the same exact bouyancy.

Sorry wargoth, I'm not trying to start an argument, merely stating my beliefs, which could be wrong.

testarossa wrote:

FYI, the clear tube spec is 3mm below the flange on the carburetor. I respectfully disagree with wargoth's assesment of the clear tube test. If it didn't work, then how does a water level work? I believe that the clear tube provides the most accurate measurement since it demonstates actual fuel level. Setting float heights with dial calipers assumes that all floats are perfect with the same exact bouyancy.

Sorry wargoth, I'm not trying to start an argument, merely stating my beliefs, which could be wrong.

+1 All floats will not have the exact level of bouyancy so the fuel level must be measured realtime with fuel in the bowls floating the floats. The clear tube test is described in detail in the Kawasaki factory service manuals. I doubt that Ma Kaw would have been telling every dealer in the world to use it if it was BS as it would not be in their best interest to have their products running like crap. Ed

Hi Testarossa,

No. I haven't had the carbs ultrasonic cleaned...they weren't too bad so I just used carb cleaner and followed some of the procedures suggested in this forum. I was a little overzealous with the cracked tubes and pulled them out before checking out how to repair them! I will either try to make new as suggested by Wargoth OR find replacement bowls at a local shop.

Thanks for the help.

Hi Wargoth,
Thanks for the step-by-step on replacing the overflow tubes...I'll see what I can find in local hobby shops otherwise I may need to find a couple of used bowls somewhere.

I have had good luck with this repair.

As far as the clear tube goes, I overstated what I actually meant to make a point. Most manuals do not have a dynamic float measurement. if you move the tube up and down at all during the test it makes it innaccurate because fuel cannot flow back out the float needle and you have increased the float bowl volume with the tube.
My Chiltons vintage manual (Motorcycle and atv repair manual 1945-1985, possibly the most useful shop manual for the vintage wrench-bender) states that the fuel level with the clear tube test is "2.5~4.5mm" using special gauge p/n:57001-208. This is a big range, while the spec for doing it the right way is 30mm or 1.2". Note that there is no + or - in this spec. Also be sure that the needle is fully seated, but the spring-loaded pin is not pushed in at all. I do this by holding the carb with the float pivot horizontal on top and the carb base flange vertical. I also use dial calipers locked to the proper measurement and use the depth rod on the far end from the dial.
Also note that the proper synch mismatch is 2cm, or approx 3/4"... not too much.
I will go get some pics and post them in a bit...