I have not seen it used on motor bikes, But for go karts and maybe some motorcycles, they have an adapter at the exhaust port that the header clips to with a couple of very strong springs. Then it can seal the exhaust, but be bumped and just maybe leak for a moment or not at all. Then the springs pull the pipe back into the center again.
I saw it up close in person at a go kart shop. It seems to be like a ball and socket kind of mechanism to make the manifold connection to the engine. Not sure if they can be purchased for the size for these engines (lawn mower type like mine) for motorized bikes.