Cracked Standpipe/Overflow and Leaky Float Bowl Repair

Maraakate

Maraakate

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Someone sent me a leaky float bowl to fix a leak. Here's how I do it.

Take a vacuum/pressure tool such as a Mityvac and put the line on the drain line. Cover the top.
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Fill the bowl with alcohol or mineral spirits. With the Mityvac set to PRESSURE try to pump 5-10 PSI in it. Look at the bowl. If it doesn't hold pressure you'll see bubbles where the leak is.
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Bubbles forming and pressure dropping.
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Hair line crack, couldn't see it before, but now I got a hint where it is.
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I used an adjustable temperature soldering iron, set it to 775F, with some flux and a pencil tip soldered it up. You almost kind of have to "sweat solder" as you'll see the pool move around. Try to get it as best as you can, then verify it's not leaking any more with the Mityvac. When I'm satisfied I clean it up with a small points file. A small blob at the bottom is fine, won't hurt it. If the hairline is completely top to bottom then you'll have to try and clean it up better. The file won't reach that low for me at the joint and because it doesn't affect anything I don't worry about it. Since this picture was taken I spent a bit more time on filing.
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Holding pressure.
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Clean up any slag left in the bowl and you're good to go. An alternative way of doing the soldering is to use a butane pen torch and sweat solder like you would a copper pipe.
 
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Thinking about this in reference to the CB450 Keihin carbs, which do not have a drain tube, just a hole in the screw. To connect pressure, one would have to make/acquire a piece of brass tubing, threaded on one end to 5mm X 1.00; maybe thread it a bit extra, so you can fit a nut and O-ring for a seal. Then take the drain screw all the way out and replace it with the threaded tube. The rest would be the same.
 
WintrSol said:
Thinking about this in reference to the CB450 Keihin carbs, which do not have a drain tube, just a hole in the screw. To connect pressure, one would have to make/acquire a piece of brass tubing, threaded on one end to 5mm X 1.00; maybe thread it a bit extra, so you can fit a nut and O-ring for a seal. Then take the drain screw all the way out and replace it with the threaded tube. The rest would be the same.
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Are you talking about the 450 nighthawk? It looks like you just attach the pressure to the drain on the bottom and then fill the bowl with alcohol/mineral spirits and pump pressure to see if the screw seat is leaky.
 
Maraakate said:
?
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Split drain tube, CB350/360

Anyone who's soldered up a split drain tube knows it's something of a PITA and even when done doesn't look particularly 'pretty' I was in traffic yesterday thinking about it and came up with something new. Couldn't find any brass tube the correct diameter to sleeve the drain tube but did find...
www.vintagehondatwins.com www.vintagehondatwins.com
 
Would be nice if you found another/similar size thin brass tube to push directly over the old one;an interference fit.. :unsure:
 
crazypj said:

Split drain tube, CB350/360

Anyone who's soldered up a split drain tube knows it's something of a PITA and even when done doesn't look particularly 'pretty' I was in traffic yesterday thinking about it and came up with something new. Couldn't find any brass tube the correct diameter to sleeve the drain tube but did find...
www.vintagehondatwins.com www.vintagehondatwins.com
Click to expand...
Ah OK. I've thought of that in the past never tried to do it that way. Good idea.

Alan F. said:
Heat shrink tubing has been known to work temporarily.
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I've heard of that. Mike said he tried experimenting with that when he first got into carb repairs as a side job and found it didn't last very long. It was mentioned by me in that thread linked from crazypj, but I wouldn't use JB weld or any other two part epoxies except in a total "stranded on the road, no cellphone" kind of emergency. Despite what people claim, JB Weld is not gasoline immersive. I've seen so many failed gas tank repairs with that stuff. And yes, they sanded, they prepped, they air dryed, squeezed the tube out for a few seconds to "purge" it, then mixed the remaining contents for a full 30 seconds, applied, waited a week... it just doesn't hold up.
 
Normally I don't do carb repairs, only modifications to allow K&N or Uni filters to be used on CB350 and CB360 (and CB/CJ250/360)
This was just a very annoying weep that I haven't seen before and I didn't have a spare float bowl.
I had heard the 5 minute epoxies won't hold up to much of anything (and from experience I believe it) but the 'slow' JB Weld has been good for almost everything I've tried it on for the last 45 years.
It has higher heat tolerance than better known fillers when doing port work (always used Devcon as that's 'the 'professional stuff' that costs about 5 times more)
I guess we will find out how well it works in a few weeks.
 
If it works for you. I have seen many failed repairs of that stuff on gas tanks and carb bodies. I'm talking regular JB Weld, not the 5 minute stuff. It seems to be a roll of the dice if it holds up or not.

If the carbs junk anyways I mean why not? The times I've seen it fail is not right away, but a few weeks later or a few months later. If you can make it past the year mark then it's probably OK.
 
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