Motorcycle customizers are always looking to set their machines apart from the ordinary, eschewing the commonly seen exhaust systems found in any aftermarket catalogue. Aftermarket exhaust pipes are bent using expensive bending machines. Don't let this discourage you. Fabricating and bending your own unique exhaust pipes is easier than it looks and can be done with a minimal investment in equipment. In fact, almost all of the tools required can be purchased from your local home improvement centre.
Sketch out the design of your custom exhaust pipes on a sheet of paper. Be sure to include how your custom pipes will bend away from the motor.
Take measurements between your motorcycle's exhaust port (the point the exhaust pipes mount to the motor) and a mounting point near the foot pegs, using a flexible tape measure. These measurements must allow the custom pipe to clear your motorcycle's frame and motor.
Create a bending jig from wood. Draw the shape of the required bends onto the top of several two-by-fours joined together with heavy-duty wood glue. This will serve as a mandrel. Cut the shape out of the two-by-fours with a jigsaw, angling the saw's blade at a 45-degree angle. Screw the shape into place on a large plywood sheet. Screw a piece of scrap wood into place near the wood shape to act as a holder for your pipe. Create as many of these jigs as needed to form the bends in your pipes.
Select a length of pipe that is at least 1 foot longer than the length required by your measurements. Cover one end of the pipe with duct tape. Fill the pipe with sand from the pipe's open end. Pack the sand down firmly with a wooden dowel to remove air pockets, then cover the pipe's remaining opening with duct tape.
Heat the pipe at the desired bending point with a MAPP gas torch until the pipe has a dull reddish glow. Place the pipe immediately between the jig's mandrel and the scrap wood holder. Grasp the far end of the pipe and pull it towards you to bend the pipe against the wood mandrel. Hold the pipe in place for 10 to 15 seconds to allow the pipe to cool slightly and hold its shape.
Remove the pipe from your jig. Repeat as needed until the pipe is bent to your desired shape. Cut the excess length from your custom pipes once all of the bends have been completed, using a grinder fitted with a metal cut-off wheel.
Dry your sand by baking it in the oven for at least 30 minutes. Removing any trapped moisture from the sand will prevent steam from accumulating within the pipe while you heat it with a torch.