| Options in Harley exhaust pipes are as great as the chest of Anna Nicole Smith. You can buy and bolt-on. Years of stock layouts from Harley — plus a rich aftermarket — let you adapt and adopt styles ranging from ol’ time upsweep to drag to collector to shotgun. If you are stubborn like me you can even ignore all that. You can make ’em. It’s not as hard as it sounds, so stay with us.
Custom-made exhausts come two ways…
First, intricate designs with tight bends (photo 1), are best fabbed from small pieces of mandrel bent tubing. (For the full run down on this method, see Easyriders, May 1995, page 126). Some caveats: careful alignment, matching and welding of the pipe sections is crucial for a uniform look. And built up pipes contain weld bead that may eventually behave, or appear, differently than the rest of the tube when exposed to heat, corrosion, time. The other route: pipes bent from a single piece of tubing (photo 2). You avoid joint and weld issues. This requires an engine/frame installation that can live with gentler bends — plus an experienced bending shop. The key to success is to make a good pattern that the shop can match. Here’s how… First obtain flexible automotive exhaust tubing (photo 3) — check large D-I-Y auto supplies, J.C. Whitney, etc. It’s easily bent by hand and cut with tin snips. Use the diameter you want your finish pipes in, and get plenty of extra length. It’s simple: bend and cut the pipes until they fit the installation to your liking. Pay particular care to a good concentric and perpendicular fit in the exhaust port, and any tight tolerances elsewhere. Remove them gingerly. Next use a utility brazing torch (photo 4) to immobilize the tubing by applying a path of molten braze down one side (photo 5). The result: a pair of pipe patterns (photo 6). It may take two or three tries. Sometimes, an additional jig assures the finish pipe matches the pattern at critical areas (photo 7).
Next is selection of pipe stock. One major choice: seamless, versus seamed (photo 8). Save a few bucks with seamed tubing. Make sure that, when the stock is bent, the seam is oriented inwards, towards the engine, to obscuring appearance differences. Now, for materials: mild steel or stainless (photo 9)? Stainless, although initially more expensive, need not be chromed for a matte finish. It will also not conduct heat down as far along the pipe. But, it does heat-yellow more readily than chromed steel. One easy pick — you can save money and stay with mild alloys; chrome-moly, 4130 or shelby tubing is unnecessary for this non structural application.
Next, perform any machining operations that require the tubing to be rotated in a lathe or metal spinner (photo 10) — like antireversion necking or flanging to fit the exhaust port (photo 11). Some can also be handled later.
Onto the pipe bender. Look for modern mandrel bending machines (photo 12) that can also handle bending in more than one plane (photo 13). A special casting metal (that melts at boiling water temperature) can hold earlier-bent sections securely in the machine. Also if needed, inquire about tube flanging or crimping (photo 14). By the way, I have seen pipes successfully bent without expensive equipment. Old masters pack them tightly with sand, plug with threaded caps (later cut off), apply heat liberally, and carefully coax in an old-time conduit or plumber’s rig.
Once the bender’s done, fit the pipes and consider mounting methods. It may be necessary to rotate each tube slightly to get the optimum appearing alignment. Since my tubes were stainless, they ran cool enough about two-feet from the port to allow the adel clamps (photo 15). Metal strap clamps give similar rotational flexibility. Next, fab exhaust port connections (photo 16). It is still possible to braze on an adapter sleeve (photo 17) to match the port or to fix misalignment.
Finally, consider your neighbors. Slip-in baffles (photo 18) reduce noise simply and effectively. Longer baffles (photo 19) are more efficient. Look for straight through, glass pack design rather than a perforated block-off (photo 20). If your local gendarmes are prone to night sticking suspicious pipes, throw in a little steel mesh for insurance!
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— Jake
