Ok… First off let me say that there are multiple ways of doing this. I have no experience with making pipes, and this is the first set I’ve made so I’m no expert. I don’t know how strong they are or if they’ll fall apart.
I’ll go into detail about how I made my pipes, but if I was to do it again (and I expect I will) I would use some different materials and techniques. On the Left is a piece of mandrel bent 1 ½” OD stainless. On the right is a piece of mild steel with the same OD bent for me at the local muffler shop. You can see that the stainless has a much tighter radius. That would have saved me a lot of work trying to get a tighter radius out of the pre-bent pieces I had made. More on that in a bit…
I primarily used three tools to make these:
I used mild steel to make the pipes. Its 1 ½” OD with a 0.083” wall. Exactly the same as the spine of an XS650 frame (convenient isn’t it?). The stock headers have the same OD so any muffler will slip right on to the pipes.
First thing I did was cut the ends off of a pair of scrap headers so I had the flanged end needed to clamp the pipes to the cylinder head. I cut it off about 1” after the pipe to flange weld.
The reason for the excess pipe was that stock headers are double walled.
Next I carefully cut off the outer pipe from the flange as close to the weld as I could. The inner pipe actually tapers out to meet the flange so it provides a perfect shape to fit inside the end of the new pipe and get a good strong weld. I then trimmed the inner pipe back a bit so I didn’t have any excess.
The flanges were fit with a metal ring gasket I got from the local muffler shop and lightly clamped into the cylinder head with the stock retainers.
I took a bunch of foot long pieces of pipe to the muffler shop and had them bent on there hydraulic machine. The problem with muffler shops is that they don’t tend to have equipment for making nice tight undistorted bends, but they do tend to do the work for free
The bent pieces were badly distorted at the ends of the bend and the OD of the pipe had contracted from being stretched as they were bent. This is where the miter saw was handy for cutting clean and square. I cut all the bends before the distortion got too bad and ended up with about ten 90 degree bends. The ends of the bends were out of round and the OD had shrunk down to much so I was able to fix the problem by hammering the ends of the pipe with a big ball peen hammer. I was lucky that the ball is of a perfect size to pound into the pipe and bring it back into shape. Once the hammer fit in the pipe I could use it as an anvil to shape the pipe with.
I spent a bit of time with a three foot length of pipe figuring out how much room I had to play with and how far out from the cylinders I wanted the pipes. Then I used some string to hang the pipe off the frame so I was able to free my hands to see how the bends would fit.
Well it turns out that the bends just were not tight enough to go from the exhaust port to the hanging pipe. The stock XS frame doesn’t give you much room to squeeze the right hand pipe between the cylinder and the down tubes. My only option was to make the bends tighter. I tried heating them but they distorted when I tried to bend them. So I decided to section them with the angle grinder and cut off disk and weld the cuts back together. I didn’t cut all the way through the pipe. Instead I left a small section at the outer edge so it was easy to tack back together. I did end up cutting some of the bends down to 45 degree sections because compound curves need to be made so the angled exhaust ports can meet up with the “parallel to the frame” pipes. (see the overhead pic of the finished pipes at the end and you will see what I mean)
Once the cuts were made I bent the edges together and welded them back up. It’s not the smoothest bend but it gets the job done. I used a Dremel tool and a small grinding stone to grind down the insides of the weld. (easy to do both sides on the 45 degree pieces)
At this point I had a bunch of bends, some 45 degree and some 90 degree (I adjusted the radius and sliced bends as I went) and I knew where I wanted the pipes to end up. I basically started mixing and matching bends and would tack weld them in place with three radial tacks whenever a piece looked like it was going where I wanted it. I started building the top pipe first AFTER I was sure I had enough room under it for the lower one. I would cut short little wedges of pipe whenever I needed to slightly change the direction of the curve. If the piece I cut didn’t quite fit I would put it aside and cut another one. In the end I used up all the pieces I cut since they would inevitably be “just right” in a different spot. I beveled the edges of every piece I cut to try and ensure the best weld I could get.
Unfortunately the OD of the bends were still a little too small compared to the unbent stock that they would butt up to so I had to reduce the OD of the straight sections. This was done in a similar way to how I tightened the bend radius. I cut four wedged slices in the end of the straight pipe, then I used a pipe clamp over the end of the pipe to bend the “tabs” I had made in slightly. Weld them up and tada!
So, that’s about it. Once everything was tacked in place I fully welded it all and then used the angle grinder to smooth out the welds. I really did make it up as I went along. Obviously properly bent tubeing would have saved me lots of time and the results would have been a lot better, but since my Father-in-law works in the pipe business I think my total cost for materials and labor was $15 and a full days work. My next set will be stainless mandrel bent and TIG welded. These ought to rot out in a month or two…
A picture is worth 1000 words, So… I’ll make this essay 4000 words longer.
I hope this helps you