Cracked overflow tube...

Two of the carbs in my 1980 kz750 were leaking gas through the overflow tubes. I took apart the float bowls to free up the float needle, but it looks like the gas is actually escaping through a crack in each of the brass overflow tubes inside the float bowls. I checked the two that weren't leaking and neither had a crack.

It also looks like this might have been an issue for the previous owner, since there's some type of putty where the tube connects to the float bowl body.

Any suggestions? I'm thinking about using some type of epoxy to seal up the crack. Maybe silicone caulk??? Maybe a two-part epoxy. I have no idea what to do if that won't work.

I would replace them rather than do a patch that may fail at night in the middle of nowhere. You should be able to finds the parts on eBay, or if not, WG can probably help. Ed

chrispysaki wrote:

Two of the carbs in my 1980 kz750 were leaking gas through the overflow tubes. I took apart the float bowls to free up the float needle, but it looks like the gas is actually escaping through a crack in each of the brass overflow tubes inside the float bowls. I checked the two that weren't leaking and neither had a crack.

It also looks like this might have been an issue for the previous owner, since there's some type of putty where the tube connects to the float bowl body.

Any suggestions? I'm thinking about using some type of epoxy to seal up the crack. Maybe silicone caulk??? Maybe a two-part epoxy. I have no idea what to do if that won't work.

Crack in tube itself might be sealed with solder, or JB Weld, or snug fit thin wall plastic hose over the tube, or heat shrink-fit tubing.

Crack or break where tube joins carb body -- best repair choice may be JB Weld, or possibly solder.

When repair is completed, before reassembling float bowl to carb, would test for flow through the tube. And assure it's not clogged with JB Weld or solder.

Could also do a search for similar threads by typing something such as "cracked overflow tube" in the search box toward top of screen on the right hand side. Probably find additional (maybe better) repair suggestions.

Good Luck!

Great ideas! It's a hairline crack along the length of the tube, so I think I'm going to try some heat shrink tubing. Do you think the gas will eat it away, though?

what carbs do you run?

I have a set of vm24's with acel pump that are junk, but the float bowls are still good... does anyone know if they will swap out?

34mm keihins. I doubt they would be interchangeable, but thanks for the offer. I decided to try the JB Weld. I'll let you know how it works out.

Any of these look like yours? Some racks of 4 are pretty inexpensive.

eBay Kawa Carbs

I had the same problem with one of my carbs. I got some very thin brass tubing at a hobby shop, cut a length, slipped it over the cracked tube and soldered the bottom.

It you use JB Weld make sure you let it cure for at least 24 hours before coming into contact with gas.

It worked! I used the JB Kwik Weld, which is supposed to have a four-hour cure time. The only difference I could see between the standard and kwik cure is that the kwik is only rated to 300-degrees and the standard is good up to 600-degrees.

That brass tube is a great idea...I thought about just soldering the existing tube, but I was worried about melting it.

I took the bike out for about 1/2 hour yesterday and so far, so good. (except now that I've finally gotten to run it more than around the block, I noticed the oil leak around the header is worse than I realized - anyone know if tightening the header bolts is a 'good enough' solution for the rest of the summer?)