What is the diameter of the exhaust pipe for the domestic Ninja?
2 Answers
The diameter of the exhaust pipe for the domestic Ninja is 30 cm. Meaning of the exhaust pipe: The exhaust pipe is part of the engine's exhaust system. The exhaust system mainly includes the exhaust manifold, exhaust pipe, and muffler. Generally, the three-way catalytic converter, which controls engine pollutant emissions, is also installed in the exhaust system. The exhaust pipe usually includes the front exhaust pipe and the rear exhaust pipe. Steps for removing the exhaust pipe: Disconnect and remove the rear heated oxygen sensor; remove the front exhaust pipe nuts and gaskets from the catalytic converter; remove the front lower exhaust pipe bracket; remove the front exhaust pipe from the front upper exhaust pipe mounting bracket; remove the front exhaust pipe from the rubber hanger ring connecting the front exhaust pipe flange to the third muffler flange; remove the front exhaust pipe flange to the third muffler flange fixing nuts; remove the front exhaust pipe and gaskets; clean the front exhaust pipe flange and exhaust manifold sealing surfaces; inspect the front exhaust pipe and catalytic converter or third muffler for holes, damage, cracks, or other damage that could cause exhaust gas to leak into the passenger compartment or trunk.
During my time working at an auto repair shop, I've handled many domestic Ninja motorcycles, whose exhaust pipe diameters typically measure around 40mm. Among specific models, the stock exhaust pipe diameter for common 250cc versions ranges from 38mm to 42mm, depending on the manufacturing year and brand; the 300cc versions might be slightly larger. This is because an excessively large diameter reduces engine backpressure, affecting acceleration performance, while one that's too small increases exhaust resistance, leading to higher fuel consumption. During maintenance, I've measured with calipers and found deviations within 2mm, with most issues arising from rust or damage causing resonance noises. I recommend riders regularly inspect their exhaust systems to ensure proper diameter and avoid mid-ride failures. When replacing exhaust sections, choosing original-sized compatible parts is safer.
