Topic: Repairing cracked overflow tubes- what do you do?

[andrewk]

Hi all,

I'm sure a lot of you have experienced a cracked overflow tube on your carburetors.  If you've had a lot of these bikes, you can spot a cracked overflow from the outside- it's the leaking carb with all the hammer divots in the float bowl.

Anyway,  the obvious solution is to replace the float bowl with a good one.  But, for the thrifty, is there anyone having any luck repairing these?  I sealed the ones on my K3 (two are cracked) with finger nail polish early on in the season, and they're just now starting to weep again.  I have tried to sweat one with solder and a torch before, and that was a miserable disaster.  I've thought of maybe using some tygon fuel line that is a size small, and using a heat gun to work it on, then trim it flush with the top.

Any of you have any repair methods that worked or that you would recommend?

[ekpent]

Seems I have read where people have used the heat shrink tubing on those. Also a product called Seal-All really is gas resistant in my experience. Give it a Google.

[754]

 I think some have slipped anothr tube over the cracked one.. you may find that at a hobby shop.

[fire113]

...go and try to solder it again, I did with a solder job and got very good results.

Good luck...Georg

[chewbacca5000]

...go and try to solder it again, I did with a solder job and got very good results.

Good luck...Georg

Hi Georg,

I have the same problem and was considering soldering what did you use as a heat source.  Small torch, soldering iron etc..

[nsargeant]

i have scuffed them up lightly before and fixed it with jb weld before.  It never leaked after that.


nathan

[Duke McDukiedook]

Jb weld will leak eventually because of the ethanol.

[Ernest T]

You can replace the tube with brass tubing from a hobby shop or maybe solder up the crack.  Use lots of flux so the solder will stick to the brass.

[crazypj]

Some of the tubes are real close to float pivot arm and can contact it causing floats to 'stick' if either tube or float has even slight distortion.
 You may find one carb doesn't fill with fuel as fitting float bowl causes float to get pushed closed

[Freaky1]

Jb weld will leak eventually because of the ethanol.

I can vouch for this, even if you use the regular JB they will leak someday, and don't even try the quick dry crap.

[grcamna2]

Seems I have read where people have used the heat shrink tubing on those. Also a product called Seal-All really is gas resistant in my experience. Give it a Google.

Does anyone have any experience w/ the heat shrink tubing ?

[ekpent]

Here is some more reading on that problem but also put 'cracked standpipe' in the search function to find more. For now I will suggest my Seal-ALL but do not think that any plastic tubing would probably hold up for too long. Soldering with the correct flux and prep would be best I'm sure.  http://forums.sohc4.net/index.php?topic=88210.0

[flybox1]

measure your stand pipe OD.
cut, solder, and ride...
http://www3.towerhobbies.com/cgi-bin/wti0093p?&C=RDA&P=6

also try your local hobby shops.

[fire113]

...go and try to solder it again, I did with a solder job and got very good results.

Good luck...Georg

Hi Georg,

I have the same problem and was considering soldering what did you use as a heat source.  Small torch, soldering iron etc..

...I used an butane gas powered soldering iron, it has good heat power and was working very well togeter with standard electronic soldering tin.
Can't find the picture after I fixed it, only the picture before.

Good luck...Georg

[wrenchmuch]

Poor solder joints generally stem from the same thing as poor welds . Poor cleaning . The crack could contain varnish from fuel . Acid flux will not clean this effectively . You should start by cleaning the tube with carb cleaner and blowing it out with compressed air . Repeat this process a few times . Rinse in soapy water . Brush a little muriatic acid on the pipe only , wait about 10 seconds and then rinse with water only . Dry with heat , brush on plumbing acid flux , and solder . You can use an iron instead of flame . I melt solder onto the tip and then and then apply the tip to the tube waiting till the solder flows out . Move along the crack repeating the process until the crack is sealed . If the tube gets plugged just drill it out . I wonder why this happens . I had a petcock tube crack as well . Is this a problem in Northern climates only or does it happen in the South as well .

[Dimitri13]

Seems I have read where people have used the heat shrink tubing on those. Also a product called Seal-All really is gas resistant in my experience. Give it a Google.

Does anyone have any experience w/ the heat shrink tubing ?

Yes. Fixed my cracked tube. Been 4 months so far with no leaking.

[feld]

Seems I have read where people have used the heat shrink tubing on those. Also a product called Seal-All really is gas resistant in my experience. Give it a Google.

Does anyone have any experience w/ the heat shrink tubing ?

I've tried the heat shrink tubing. Worked for a day or two and then started leaking again. Didn't get around to pulling the float bowl for two weeks after that (at which point the carb was no longer dripping, but instead was dumping fuel) and when I did, I saw that the heat shrink tubing had expanded to larger than it had started before I applied it and it had become a bit gelatinous. So I guess you can use it in a pinch for a quick, temporary fix, but i wouldn't do it again as I don't like the idea of something like that floating around in there and/or dissolving into my fuel.

I ended up soldering the tube. I guess I didn't do a great job as it still has a slow drip, but it is worlds better than it was before. One thing that can be tricky is the float bowl acts like a giant heat sink, sucking heat away from the brass tube so you have to make sure you get the brass tube hot enough that the solder flows into the cracks and not just hanging out on the surface or you wont be making a proper seal.

My next step will be to try what I have seen recommended elsewhere here and finding some thin, hobby brass tubing that has an ID that matches the overflow tubes OD and tap it over it.

[crazypj]

I think some have slipped anothr tube over the cracked one.. you may find that at a hobby shop.

 That's what I've done a few times, soldering works but can be a bit fiddly though
You also have o be careful to make sure the floats don't catch on tube, there isn't much room in there

[feld]

Yeah, I had an issue with another float bowl that it looked like the PO replaced the overflow tube with slightly larger diameter tubing. The hole in the top of it was too large and didn't taper in like the stock tube does and my float seemed to snag on it.

I got frustrated trying to fix it and ended up buying a new float bowl from forum member harisuluv. That was by far the best "fix" I've found to date.

[jtb]

Andrew, is this a bowl from your F2?  if so, I may have one.
John

[jamesb]

Clean the tube real good and use solder it works good but you need a good clean surface to work with. I've done two of mine and haven't had any problems with either bike. I just used a solder gun.

[750K]

Ive never had to fix a cracked tube, but I've pulled out the broken stub of a couple tubes. What works really well is a small mm tap that fits inside the broken tube. The tube is press fit in the bowl and the tap grabbing inside the id of the tube allows you to twist and pull it out very easily, hopefully I'll be able to find some thin walled tubing at a metal supply or Hobbie shop.

[Duke McDukiedook]

Seems I have read where people have used the heat shrink tubing on those. Also a product called Seal-All really is gas resistant in my experience. Give it a Google.

Does anyone have any experience w/ the heat shrink tubing ?

I did, it is still running.

[Robbnc]

I used heat shrink a year ago, no problems so far.

[grcamna2]

Poor solder joints generally stem from the same thing as poor welds . Poor cleaning . The crack could contain varnish from fuel . Acid flux will not clean this effectively . You should start by cleaning the tube with carb cleaner and blowing it out with compressed air . Repeat this process a few times . Rinse in soapy water . Brush a little muriatic acid on the pipe only , wait about 10 seconds and then rinse with water only . Dry with heat , brush on plumbing acid flux , and solder . You can use an iron instead of flame . I melt solder onto the tip and then and then apply the tip to the tube waiting till the solder flows out . Move along the crack repeating the process until the crack is sealed . If the tube gets plugged just drill it out . I wonder why this happens . I had a petcock tube crack as well . Is this a problem in Northern climates only or does it happen in the South as well .

I like your idea of prep & cleaning well wrenchmuch