Consists of three steel reeds that are normally in the closed position. When pistons travel downward in the cylinders, the air in the crankcase is compressed and pressure in the crankcase below the pistons increases.
- Standard size diameter
- Pressure causes the reeds to open, allowing the air and oil mist in the crankcase to escape into the cam chest
- When pistons change direction and begin traveling back upward in the cylinders, a vacuum is created in the close, preventing air from entering the crankcase
- A slight vacuum is maintained in the crankcase and oil scavenging is greatly improved