A motorcycle's exhaust system has a very direct task: to transfer the hot exhaust gases from the engine to the rear of the bike. On all Environmental Protection Agency-certified vehicles, the system is composed of four typical components -- the header that mounts to the engine, the catalytic converter that cleans the exhaust gases, a muffler that lessens sound and the piping that connects the pieces. This is where the similarities end. Every vehicle's exhaust system is designed differently. The routing varies, as do the dimensions of each component. In case a repair is needed, knowing the size of the exhaust pipe is the first step.
Locate a straight section of pipe at least 4 inches from any juncture. Do not measure at any bends or where the pipe enters the muffler or catalytic converter.
Measure the outside diameter of the pipe. If you are using a caliper or micrometer, place it over the pipe and read the measurement. This is the outside diameter of the pipe. If you are using a tape measure instead, wrap the tape measure around the pipe and divide this measurement by 3.14 to get the outside diameter.
Measure the exhaust wall thickness at the exhaust pipe tip. Subtract this from the outside diameter measurement to obtain the inside diameter, which is the measurement by which piping is sold.
The caliper is the best tool to use for this task.
Do not measure a hot exhaust system; severe burns can occur. Wear safety glasses to prevent rust and dirt from falling in your eyes. If you need to elevate the vehicle to measure the exhaust, support it with jack stands or an appropriate ramp.