Carbs leaking from overflow tubes- my solution

So, I've been working on a '78 KZ1000B2 LTD this past fall, and discovered during the rebuild that I could not stop two of the carbs from leaking, no matter what I did with/to the float valves. I am pretty familiar with bikes in general as I worked as a mechanic from '73 to '81 for a couple of dealers (only one Kawasaki dealer though!). I cleaned and cleaned and adjusted and measured, but could not stop it.

Found this site, and proceeded to look at the index and see what any other members might have seen, and low and behold, others have had this happen also (KUDOS and thanks to Patton and others, your instructions on how to determine that the overflow tube was leaking was/is very good!). Didn't want to just a question that had been answered a dozen times already.

Sooooo......... I found the overflow tubes on the 2 suspect float bowls were indeed cracked, and a third looked like a brass-hungry woodpecker had been inside it looking for dinner.

See pics (hopefully) attached. The cracks are a very thin, barely seen line in a couple of them. The last should be the "holy" one (which was not leaking!!

Well, what to do? As has been suggested, the very best fix is replacement with a solid, good, known float bowl. However, as far as I can see, that is not a purchasable part number. You want a new float bowl, you buy entire carburetor. You buy second-hand carburetor from eBay, you can't be sure if what you get isn't as bad as what you've got.

Solder it up? Next best thing probably. Unfortunately yours truly is not that good at that (it's been awhile....).
I thought perhaps I could get some slightly oversize tubing and slide it down over the existing tube down to the alloy bowl, using a bit of Loctite or JB Weld (which someone here I think suggested??) to adhere it is place.

But then I conferred with the local shop, man named Jim Hale (props here and now to him), who provided me with what I thought is a viable solution. And that is to slide a slightly smaller brass tube up inside the overflow tube. I measured the tube ID and OD with calipers, and as it works out 3/32" is a VERY SNUG fit up inside the overflow tube. It also, at least on mine, seemed to be almost exactly the same ID as the hole at the top of the overflow tube, so I don't believe I am restricting the circuit, should it be needed.

My local hobby shop closed down, so I got these items online, a small tubing cutter and 3 pieces of 3/32" tubing. Again, pics attached.

Gotta say, that forth pic is pitiful. :ohmy:

I used the tubing cutter to trim off a length of the tubing that would go right up to the top of the existing overflow tube, where it would be stopped by the edge that had been rolled over by the manufacturer (probably done when they cut the tube, they just didn't bother to trim the inside at the top.). I cut them just short of the bottom spigot where the hose attaches, I have to look up inside to see the end of the new piece.

I mixed up a small batch of JB Weld , inserted the (cleaned up) end of the new tube at the bottom, spread a bit of epoxy around the length, and gently pushed the tube up inside until it hit the other end. Cleaned up the excess epoxy and then ran my jet cleaner up through it to get any excess out of the inside, making sure it was good and clean and clear. Used the magnifying glass to make sure it was all clear.

I'm showing one float bowl with a just-cut piece slid part way into the overflow tube. I did all 4 this way.

Final fuel level check went fine. I used the fuel level tester I bought from Z1 Enterprises to check, and from the instructions they sent with it and the manual, I think I'm good. Using an auxiliary tank I fed carbs 1&2, and then 3&4, saw no leaks from any of them.

My understanding is that the JB Weld is pretty fuel-proof, and there is such a small area (from the crack) for gas to seep into that it should not be a problem. If this ultimately fails, I may be back to searching for new float bowls.

Anyway, so far so good, although it will be a few months before I get it on the road for a real test.

Yeah! And that was one that actually WASN"T leaking!!

Probably just a matter of time though.

Nice job on fixing those tubes. I'm working on rebuilding two sets of Keihin CV34 carbs and 7 of 8 float bowls have cracked overflow tubes.

I've posted previously on how to fix these... www.kzrider.com/forum/3-carburetor/60563...at-bowl-leaks#759101

-I use a drill chuck around the old tube and then spin and pull it out.

-The closest size tubing is a few thousandths smaller than the original so I use a the back end of a drill bit with a slight taper ground into the lead in to flare out the new tube a little on the end.

-To roll over the end of the end of tube I again chuck it up in the drill, and then spin the tube while pressing the end into the dimple on the side of a threading die.

-Last step is to press the new tube into place on the float bowl.

This is my solution, took 15 minutes to make, seal with a bit of plumbers tape

Nice job.

You can get structural barss tubing in metric sizes too. Sometimes you can get a small batch on ebay. You might also get it at McMaster Carr. They have some metric brass tubing. You might have to buy a 4-foot section of it, though.

loudhvx wrote: Nice job.

You can get structural barss tubing in metric sizes too. Sometimes you can get a small batch on ebay. You might also get it at McMaster Carr. They have some metric brass tubing. You might have to buy a 4-foot section of it, though.

I looked for metric tubing and couldn't find any in a suitable size. The needed size is something like 3.3mm OD and most places that sell metric tubing only sell in 3 or 4mm (even number) sizes.

Nessism wrote:

loudhvx wrote: Nice job.

You can get structural barss tubing in metric sizes too. Sometimes you can get a small batch on ebay. You might also get it at McMaster Carr. They have some metric brass tubing. You might have to buy a 4-foot section of it, though.

I looked for metric tubing and couldn't find any in a suitable size. The needed size is something like 3.3mm OD and most places that sell metric tubing only sell in 3 or 4mm (even number) sizes.

How convenient. Sounds like they are using some oddball proprietary size or maybe it's some weird Japanese industrial size.

Kevski-

Now THAT looks like a real professional fix for the problem. I gather you turned the piece down from a solid piece of brass? You must have had to also thread the float bowl after you pulled the small 'spigot' out (pressed in? threaded?)?

Anyway, this never occurred to me to do, and I am not a machinist by any means, nor do I have access to a lathe, but it seems a very solid fix.

All shows the value of forums like this one.

KUDOS!