[24 October 2007]
The gas tank didn't work out as I had planned.
I set about brazing all the holes left and pouring gasoline in it to spot any leaks. I got most of the holes by the blowing air + soapy water method; I only found four more by using the gasoline-test. I got to a point where I had only one hole left that was a couple inches inside the front center channel, and I couldn't get it to stop leaking. The brazing would always form a crack in it whenever it cooled in this spot, and every time I re-tried, the crack got a bit longer than before. Plus I also noticed from repeated test-fittings that the front channel of the tank was squeezing in and getting narrower, to the point where it almost wouldn't fit over the bars of the frame anymore. The bike frame tubing is 1-inch outer diameter, and the tubing I cut in half to make the center channel of the tank is 1.25-inch outer diameter, so there should have been plenty of room--there was plenty of room, when I first made the center channel, and before I welded the sides on. One of the problems of welding metal is that it tends to shrink slightly from when you first started. I figures that a quarter-inch would be enough free space to allow for that, bit I ended up being wrong there and over the course of trying for three days I only ever saw these cracking and pinching problems get larger. I didn't think that there was any way to realistically weld or braze it, the area was already a mess and it was difficult to reach with much of any tools. I thought about coating the area with some epoxy resin but decided that since the tank channel was so pinched already, that there was already a lot of stress on the metal, and that it simply wasn't going to be dependable in holding liquid fuel. If I tried to simply weld another patch over the whole 1" diameter area now, then the front of the tank would no longer fit around the frame tube, and then it really wouldn't be of much use at all.
I didn't think that I had time to start over and make a new tank before the weather got cold, and I wanted to go on at least a couple rides before it snowed. The last couple major things to do was make something to carry more fuel and make something to carry tools in, and I didn't feel like tossing the tank out as it had taken quite a while to do, and I did like how it generally looked--so I decided to use the tank as the toolbox instead and mount a gas can where the tool box was originally planned, under the seat on the side opposite the engine.
The photos below show the gas can in its bracket; I expect I'll be painting the gas can dark blue with the rest of the bike (I know of no US law that says they must be red, just that they must be "approved containers" and painting it blue doesn't change that as far as I know). I don't believe that it will be necessary to use anything to tie the gas can in; I had a water bottle mount temporarily on the seat tube for a medium-size MSR fuel bottle, and even though the MSR bottle didn't fit in quite right (it is too tall, and the sides are straight) it never seemed to be in danger of falling out with the general cruising I did.
The images below show the gas-tank-toolbox. The latches I found at Lowe's, I had wanted the sort of latches that toolboxes had but the only metal toolboxes that had them cost at least $40, and I didin't want to pay $40 to cut up a tolbox for a couple latches. These latches work quite well overall.
With this gas can arrangement it might be possible to connect longer gas lines to the engine and have it draw fuel directly from the bigger gas can, but I plan to just stop and dump more fuel into the tank for now. I suspect that if I had it connected this way and I filled the gas can up all the way it would be too high and would likely siphon into the carb.
I did like the way the tank looked, in that it hides the top tube from the sides. I think that when I try to do this all over again, I'll still do it this way, but instead of one tank with a deep channel formed in it, I'll make two separate side tanks that are held on by brackets that hang off the frame top tube. That way the two separate tanks will be conventional "box"shapes, and the mounting bolts and brackets holding them on will be hidden as well.
At this point all that is left to do is the kickstand clip needs a bit of help, I need to make a rear light bracket and the cleanup and painting. I had some bullet-style lights I had modified and planned to use with the bike lights but those would add quite a bit more hassle, so I'm just going to take the easy way out and use regular dual bicycle lights front and rear--Cateye EL530 headlights and Planet Bike Superflash taillights. This thing's got a number of errors now and I don't really feel like sweating over the details much more.