Flying Horse 48cc/66cc/80cc 2-Stroke Motorized Bicycle Engine Intake/Exhaust Stud &ndash; Gas Bike Exhaust and Manifold stud The Intake / Exhaust Studs hold your muffler and intake manifold to your 2-stroke 48cc or 66/80cc motorized bike engine Installation requires extracting your existing studs with a stud extractor. Once extracted, replace the stock studs with these new studs. Mount your muffler or carburetor and you're ready to ride