Replacing the Overflow tube
Here is a article that LRCXed (Larry) wrote on replacing overflow tubes in the float bowl.
As most of you know, the float bowl overflow tubes can leak due to splits lengthwise or cracks at the base of them. The split is the most common problem with most of them though. Most of the time soldering them or using JBWeld can stop the leak. But there are times that it won't work. The following is a process I have been using for a couple years now on replacing the overflow tubes.
Due to the size of the brass tube in the bowls being a bit larger than the available 1/8" brass tube available at hobby and home stores, pulling the old tube out and replacing it isn't a direct fit. The 1/8" tube is too small to fit tightly enough. Fear not, I have a cure for that.
OK, here's the two common problems with them. As you can see someone has tried to solder the tube up in the bowl on the left. The problem with this method is that if the split goes down into the section of the aluminum bowl, there's no way to get the solder to seal and bond to the aluminum bowl. Resized to 45% (was 1023 x 685) - Click image to enlarge
As for the one cracked off at the base, it can be a real pain to get that little nub out. I've used two methods. First I try driving in a couple threads of a drywall screw so it'll grab onto the brass enough so I can mount the bowl in the vice and pull it out. You'll see that in a minute. Resized to 45% (was 1023 x 685) - Click image to enlarge
If that doesn't work, I use a #30 drill bit, .127" to drill out the brass. Usually as the bit starts to cut it will grab the bottom section of it and it all comes out cleanly. Resized to 45% (was 1023 x 685) - Click image to enlarge
OK, this is how I remove a tube from the bowls. Using a pair of visegrips I clamp down on the tube just below the top of it. Then I place the bowl in my vice just under the lip of the clamping plates. Don't tighten it up much. Just enough to hold it in place. Resized to 45% (was 1023 x 685) - Click image to enlarge
Now using a long sturdy screwdriver I pry up quickly and the tube pops out. Resized to 45% (was 1023 x 685) - Click image to enlarge
Now it's time to make a replacement tube. Yes, I use the 1/8" brass tube that you can get at hobby and home stores. But there IS a way to make them fit. You'll see that soon. Don't you just hate suspense! Fortunately I have a metal lathe that makes this whole process easier than using a drill. The following might work with a drill but I haven't tried that.
The first step is to round over the end of the tube for the top of it. Clamping the tube in the jaw, I have a metal rod that I drilled a counter sunk recess in the end using one of those counter sinking bits. Resized to 45% (was 1023 x 685) - Click image to enlarge
After applying some oil on the tool I start up the lathe at high speed and hold the tool to the end of it using as much pressure as I can. Rocking it back and forth at the same time will round over the end a reshape the brass. There's no need to get the hole as small as the factory ones. It's basically small so that it doesn't catch fuel if it's just splashing around in the bowl. Kind of a limiting restriction if you will. Resized to 45% (was 1023 x 685) - Click image to enlarge
OK, now the end is rolled over. Resized to 45% (was 1023 x 685) - Click image to enlarge Now it's time to cut the tube to the length of the one you pulled out. If you don't have a full length one due to it's having been cracked off, the length is 1.515" to 1.520". I use a small tubing cutter. But you can use what ever method that works for you. Resized to 45% (was 1023 x 685) - Click image to enlarge
NOW for the trick that makes it fit into the bowl again. I put the tube back in the lathe so the bottom end shows about 3/8". Then I put a #36, .105" drill bit in the drill chuck so the blunt end is sticking out. I also file down that end so that it's got a slight tapper on the tip of it. Resized to 45% (was 1023 x 685) - Click image to enlarge
Now I apply a little oil and run the bit in the 3/8". This expands the brass out to the size needed so it will fit tight in the hole again without leaking. As you can see the tube has expanded slightly. Resized to 45% (was 1023 x 685) - Click image to enlarge
Now I file a slight tapper on the end of the flared tube so it'll slide into the bowl with now hangups. Resized to 45% (was 1023 x 685) - Click image to enlarge
It's time to put this new tube into the bowl. But as I type this I realize I forgot to show you that you should index the height that the tube sticks up with something for reference. I use a piece of 1/4" ID metal fuel line. The OD is 5/16". When you lay it across the bowl and look at it level you'll just barely be able to see the tip of the tube when it's in at the right height. Resized to 45% (was 1023 x 685) - Click image to enlarge
To install the new tube I have a set of aluminum plates I set on the vice. In one of them I drilled a 1/8" hole. It doesn't go all the way though. It's there so that when I tighten up the vice to run the tube in, it doesn't smash the rounded over end. Resized to 45% (was 1023 x 685) - Click image to enlarge
Aligning the bowl and the tube horizontally between the jaws of the vice, I slowly tighten up on it making sure it stays aligned so I can press the tube in the hole. It's a tight fit. It needs to be so it doesn't leak or vibrate out. You may need to keep the two aligned by hand as you press it in. Go slowly a little at a time. Stop and check to make sure your not going in too far by using what ever gauge you set up for height reference. Resized to 45% (was 1023 x 685) - Click image to enlarge
And that's it. You now have a new overflow tube that's not covered in goop or solder. Resized to 45% (was 1023 x 685) - Click image to enlarge
I hope this helps those that have had problems fixing the leaks in their bowls. Like I said, I've been using this method for a couple years now and have had no problems or returns. Many sets of carbs that I have done for members here have these repair tubes in them and they don't even know it.
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