An upgraded exhaust can improve the look and sound of a bike. It can also increase performance by freeing up air flow, but only if properly tuned.
OE manufacturers are constrained by budgets, so they may use an exhaust design that doesn’t allow the engine to breathe properly. This means the ratio of fuel to air becomes imbalanced.
Design
The exhaust system plays a multi-functional role in the performance, efficiency, and style of a motorcycle. Its primary function is to efficiently remove waste gases produced during the combustion process. This improves engine health by reducing overheating and fuel vapor while also boosting torque.
The stock exhaust on most bikes is designed to comply with regulatory guidelines such as noise and emissions. While it does a great job of walking the line between performance and fuel economy, it may lack certain desirable characteristics like power gains or a unique sound.
Upgrading the exhaust is a cost-effective way to achieve these improvements. The first step is determining the design of your custom exhaust. This can be as simple as a straight pipe or a header with a baffle. The header is usually a longer tube that connects to the engine. It can be tucked tightly against the engine or bent into a wild, custom design. The flange and header tubes are then tack welded together.
Materials
The design of a custom exhaust for bikes take into account many variables including engine performance, packaging limitations, materials available and fabrication techniques. Many of the high-performance exhausts are a significant departure from the OEM design to allow for better flow and reduce back pressure. These systems typically weigh less than the factory muffler and can save several pounds of weight on a bike.
A good starting point is to take measurements of the space where you want the exhaust mounted. Use a poster board or another large sheet to make a template and mark the measurements on it with a pencil or marker. You should also take the measurements of your foot pegs and seat for proper positioning.
The pipe’s length and diameter are critical to engine performance. Short pipes run the bike lean and should be jetted for a richer fuel mixture in carbureted bikes, while a long-pipe runs the engine inefficiently and should be re-mapped in fuel injected bikes.
Welding
Whether it’s a pipe hanging from the frame, or a tab that goes behind the foot peg, it has to be sturdy and hidden. It can be made from anything from solid bar to angle iron, cast metal or sheet. It must be able to support the weight of the pipes, or it will crack under stress.
When it comes to welded exhausts, TIG welding is the preferred method. This allows for fine control and penetration, resulting in a smoother weld bead. MIG welding is acceptable as well, though it requires a lot more practice to achieve a good look.
After taking measurements of the bike, including where the pipes are going to mount on the frame, a template is drawn out on poster board with a thick marker. This model is then used as a guide for the actual fabrication of the custom exhaust. This ensures that the new exhaust will fit properly and clear all necessary parts of the motorcycle.
Finishing
Once the welding is complete and the pipes are cleaned, they are ready to be installed. A custom exhaust can be a real show stopper and add a whole new look to a motorcycle.
When building pipes, it is important to know what you are doing and plan your work thoroughly. There is a fine line between increasing power and reducing fuel economy. To achieve a good balance, it is recommended to consult an expert or use a premade system.
The OE and aftermarket manufacturers put a lot of time, money and effort into developing their systems and they buy their supplies in large quantities. This enables them to offer high quality products at very reasonable prices. If you are willing to do the research, and have a little patience, you can build a set of pipes that will make your bike stand out in a crowd. Just don’t run out of argon before you finish your project!