CB350F - Carbs keeps overflowing

Well, I might give soldering a try then, and if not sucessful, use JB Weld.
I do have a small butane lighter/torch which should be perfect for heating up the tube before applying solder with my soldering iron. I do have electronics flux and solder. But can't seem to find plumber flux and solder here in France, or I have no idea how they call that in french...

As for cleaning the tube, I think I'll just use my dremel with a copper brush on it, and then put the bowls in my ultrasonic cleaner which make a great job for cleaning fuel residues.

Hope this is easier than soldering PCB boards which I'm no very good at lol
I do have 2 bowls with long cracks that are about 3/4 of the lenght of the tube.

Forgot to mention that fuel here does not have ethanol in it, well at least I always use the more expensive one without ethanol in all my bikes
 
The flux is more important than the solder as far as electronic/plumbing. If you can find a radiator shop, they could do it in five minutes. If you can Amazon, they should have the flux and solder. If using an electronics iron, don't try it with a circuit board iron. Use one that you could dolder two 2mm diameter wires together with. Cleaning inside the crack by scratching the length of it with a small file (you won't get in it, but will make a clean metal edge on both sides). Flux immediately. Then heat and flow in the solder.

I'm too old, shaky, and blind for PC board work now. The last few years at work, I had co-workers that would do it for me. I hope that I don't have need for that anymore now that I've retired.
 
You will want this flux or something similar if you can find it. You won't want to use a soldering iron to solder this, just a torch. You'll brush on the flux and heat it until its more or less gone. This will leave a perfectly clean surface for your solder to adhere. Then continue to heat the tube (from a bit away - it doesn't have to be red hot) and contact the solder to the tube. If it doesn't flow, get the tube hotter.

192425.jpg
 
AdvCo is right on with the flux - this is what I used. If using a torch, keep swiping the tube with the solder until it melts and flow to judge the correct temp. I guess that since my iron is butane powered, it worked well for this. I agree that a circuit board iron will not.
 
Do we even know that the overflow tubes are cracked or leaking? He posted on page one that he didn't see any cracks and now there are 2 pages going back and forth about epoxies and solder. It's pretty rare that these things crack. Yes, it happens, but not often. I've rebuilt hundreds of carbs and I've yet to encounter a single cracked overflow tube. I've had many instances of needing to polish up or clean the float valve, and even more instances of just needing to tap the bowls with the handle of my screwdriver.
 
irk miller said:
Do we even know that the overflow tubes are cracked or leaking? He posted on page one that he didn't see any cracks and now there are 2 pages going back and forth about epoxies and solder. It's pretty rare that these things crack. Yes, it happens, but not often. I've rebuilt hundreds of carbs and I've yet to encounter a single cracked overflow tube. I've had many instances of needing to polish up or clean the float valve, and even more instances of just needing to tap the bowls with the handle of my screwdriver.

Quote on page 1 from OP

tahitianrider said:
Well you guys were right, turns out 2 bowls had cracked tubes. Found out an easy to test them: put your finger on one side then spray carb cleaner with a small tip on the other side and see if it leaks.
One thing weird though is that one that wasn't cracked stopped leaking just by putting it on another carb lol

But on the 8 bowls I have (I have 2 set of carbs for CB350F), at least 3 are cracked.. so I guess they can be fixed with the plumber solder thing?
Could an electrical heat shrink tube over the tube work??


I really don't think its very rare. He has 3/8 bowls that are cracked. I had 2 bowls with cracked overflow tubes on my 360, which was the 3rd bike I ever owned. Trek had 150 cracked overflow tubes on the 400a. The first one that I had crack was good in the fall, no leaks whatsoever, and in the spring had a 1" hairline crack after sitting on a shelf empty. Maybe it has something to do with the cold? Idk.
 
advCo said:
Quote on page 1 from OP


I really don't think its very rare. He has 3/8 bowls that are cracked. I had 2 bowls with cracked overflow tubes on my 360, which was the 3rd bike I ever owned. Trek had 150 cracked overflow tubes on the 400a. The first one that I had crack was good in the fall, no leaks whatsoever, and in the spring had a 1" hairline crack after sitting on a shelf empty. Maybe it has something to do with the cold? Idk.
I missed that post. Two posts before it he said they weren't cracked. And I had no idea Trek went through 150 carbs on his 400a. That's a lot of money and a lot of carbs. But like I said, I have never in 30 years and hundreds of carbs ever encountered a cracked tube. Even on all three 360s I built. So, for me they are rare.
 
advCo said:
You will want this flux or something similar if you can find it. You won't want to use a soldering iron to solder this, just a torch. You'll brush on the flux and heat it until its more or less gone. This will leave a perfectly clean surface for your solder to adhere. Then continue to heat the tube (from a bit away - it doesn't have to be red hot) and contact the solder to the tube. If it doesn't flow, get the tube hotter.

192425.jpg

I'll just use my butane torch lighter then!
Holy cow that flux cost $60 on Amazon in France,
Would this one do the job too?
718-BhFStCL._SL1500_.jpg


I missed that post. Two posts before it he said they weren't cracked. And I had no idea Trek went through 150 carbs on his 400a. That's a lot of money and a lot of carbs. But like I said, I have never in 30 years and hundreds of carbs ever encountered a cracked tube. Even on all three 360s I built. So, for me they are rare.

Yeah I didn't spot the cracks upon first inspection because they were thin and tubes were all shinny coming out of my ultrasonic cleaner, but did notice them when I sprayed carb cleaner throught them.
Well, I haven't rebuilt many carbs but this is a first for me, but 3 out of 8 bowls though
 
tahitianrider said:
Would this one do the job too?

It looks like that flux paste should be fine. Whatever you do, you will want the paste, as liquid is quite messy and makes it difficult to tell what you're actually putting flux on. Solder will tend to flow to any area that has been fluxed within the proximity of your repair, so you want to use very little flux.
 
irk miller said:
I missed that post. Two posts before it he said they weren't cracked. And I had no idea Trek went through 150 carbs on his 400a. That's a lot of money and a lot of carbs. But like I said, I have never in 30 years and hundreds of carbs ever encountered a cracked tube. Even on all three 360s I built. So, for me they are rare.

Yeah Irk it got to be rediculous I tried replacing the tube itself, shrink tube, solder held for a month or so, tank liner worked for a few months. Then one let go. Thankfully Cxman got to feeling so sorry for me he sent a beautiful pair.
 
trek97 said:
Yeah Irk it got to be rediculous I tried replacing the tube itself, shrink tube, solder held for a month or so, tank liner worked for a few months. Then one let go. Thankfully Cxman got to feeling so sorry for me he sent a beautiful pair.
Why in the hell would you go through 150 carbs?
 
irk miller said:
Why in the hell would you go through 150 carbs?

Lol, I just threw a high number in there because I knew he went through hell finding a good set.
 
advCo said:
It looks like that flux paste should be fine. Whatever you do, you will want the paste, as liquid is quite messy and makes it difficult to tell what you're actually putting flux on. Solder will tend to flow to any area that has been fluxed within the proximity of your repair, so you want to use very little flux.

Understood, I have ordered it! I'll see if I managed to solder this off
 
WhyNot said:
How long have they been holding?
Three months. I just got it rideable last month, but the engines has been running since December. I've read on CB forums of them lasting years. If they start laeaking again, I'll just reflow.
 
Damn my carbs that were no longer leaking when testing out of the bike now leak a bit again on the bike so I guess one of the bowls still has a small crack or bad float valve.
Is it possible also that carbs will overflow when supplied by a workshop fuel line, which as a flow about 4x times bigger than the fuel petcock?

Anyway, I tried soldering the "worst" tube I have, it was cracked all the way, really all the way.
I used flux and my butane torch lighter, I was surprised with how "easy" it was on the middle and upper section of the tube, however, the crack a the bottom neat the bottom of the bowls still isn't fixed and I can't get solder to stick down there, plus it is difficult to reach with the torch & tin wire.
 

Attachments

  • crack.JPG
    crack.JPG
    34.3 KB · Views: 316
  • crack2.JPG
    crack2.JPG
    36.4 KB · Views: 318
Probably just need more heat on the aluminum.

As the aluminum acts like a heat sink, drawing it out fast.

and Clean the residue out of that O-ring groove.
 
Yeah that is probably the problem, I've tried soldering another bowl, even with a ton of heat on the bottom of the tube I can't get solder to melt down there. Which is sad because all the tube is perfectly soldered and looks really nice.
I think I'll just JB weld the bottom of the tube and keep the solder on the tube itself.

Yeah I have cleaned the bowl itself since I removed the oring yet, I will.
 
Back
Top Bottom