A motorcycle exhaust consists of a header pipe that attaches to the exhaust manifold on the front of the engine, as well as a muffler and a tail pipe. The key to an efficient exhaust system is the degree of bend in the header pipe from the engine toward the underside of the motorcycle. If the bend is extreme, it creates backpressure that affects engine performance. The ideal exhaust has a straight section of header at the exhaust manifold that transitions to the bend. You can build your own motorcycle exhaust using steel alloy tubing.
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Things you need
- Steel alloy tubing
- Exhaust pipe header flange
- Muffler and tail pipe
- Tubing bender
- Flaring tool
- Bench vice
- Flat file
- Welding equipment
- Exhaust gasket
- Socket and ratchet
Select steel alloy tubing with an inside diameter that matches the inside diameter of the exhaust port on the engine. Purchase an exhaust pipe header flange that matches the outside diameter of the tubing and include an exhaust gasket. Purchase a muffler that sleeves onto the steel alloy tubing and has an integral tail pipe.
Place one end of the steel tubing into a tubing bender. Make a right-hand 90-degree bend three inches from the end of the tubing. Measure the distance from the centre of the exhaust port to the underside of the motorcycle frame. Mark this same distance from the 90-degree bend and make another right-hand 90-degree bend in the tubing at this point.
Position the tubing next to the motorcycle and align the end of the three-inch section with the exhaust manifold. Note any adjustments needed to ensure that the long section of the tubing resides just below the underside of the motorcycle frame. Use the tubing bender to make the necessary adjustments. Flare the end of the three-inch section with a flaring tool.
Determine the best location for the muffler at the underside of the frame. Mark the point where the muffler will connect to the tubing. Reposition the tubing next to the motorcycle and transfer the mark to the tubing. Secure the tubing in a bench vice and use a hacksaw to cut the tubing at the mark. Use a flat file to remove any burrs on the inside and outside of the cut end.
Sleeve the exhaust pipe header flange onto the cut end of the tubing and slide it against the flared end. Lay the tubing flat on a workbench. Sleeve the short end of the muffler and tail pipe assembly onto the end of the tubing. Make sure the tail pipe section will be at the end of the exhaust system. Weld the muffler and tail pipe assembly to the tubing and allow the weld to cool completely.
Position the exhaust assembly on the motorcycle. Slide the pre-drilled holes in the header flange onto the exhaust manifold studs and put nuts on the studs to temporarily hold the end of the exhaust pipe. Mark points along the exhaust for attachment tabs that weld to the frame. Make sure to mark each end of the muffler for a tab. Remove the nuts from the exhaust manifold studs.
Secure the exhaust in the vice with the tab marks facing up. Cut random pieces of 1/8-inch thick steel as tabs. Depending on the motorcycle, the tabs will be approximately 3/4-inch long. Weld one end of each tab at your marks and allow the welds to cool.
Put the exhaust gasket on the exhaust manifold. Attach the header flange to the manifold studs by tightening the nuts with a socket and ratchet. Use wood blocks to support the exhaust in place on the underside of the motorcycle frame. Weld the tabs to the motorcycle frame and allow the welds to cool.
Tips and warnings
- Select a muffler with a catalytic converter if required. The precise exhaust pipe configuration depends on the particular motorcycle.
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