Exhaust Flange Yasuni R4 Derbi

YASUNI R4

The Spanish brand was originally known in MotoGP, when two-strokes dominated the discipline, but has also built up an excellent reputation with high-quality exhausts for 50cc motorcycles, including the Yasuni R4.

PERFORMANCE YASUNI R4

This exhaust offers excellent performance starting at medium RPMs and remains consistently powerful up to very high engine speeds. The Yasuni R4 is the perfect fit for all high-end racing cylinders with a displacement of 84 to 94 cc.

Due to the large volume, it is recommended to install it in combination with a carburetor with a large diameter, such as a PWK 30, a large-volume tuning reed valve and a reinforced clutch to prevent the clutch from slipping.

The more power and displacement, the higher the number of the Yasuni R exhaust should be selected: Yasuni R1, R2, R3, R4...

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!