Restrictor Flange f. header pipe Derbi / Gilera / Aprilia

Exhaust flange

The exhaust flange provides a stable, sealed and separable connection between the exhaust and the engine.

Function of the exhaust flange

Depending on the engine type, the exhaust flange is attached to the cylinder by means of bolts or by press-fitting. It is then fitted into the exhaust pipe and held in position by two exhaust springs, thus maintaining a certain flexibility. To ensure tightness, there is normally an exhaust gasket. Thus, the flange provides a secure and at the same time flexible connection between the cylinder and the exhaust.

And what is an exhaust restrictor?

Many 50cc scooters and motorcycles are factory equipped with an exhaust / manifold restrictor. This restriction reduces the diameter of the exhaust flange, which restricts the performance of the exhaust. This restriction was introduced to comply with noise emission regulations and to limit the speed of 50cc scooters and motorcycles.

Many riders remove this restriction to improve the performance of their two-wheeler. However, the gain in power then leads to the loss of the homologation, so beware!