Silencer Pro Circuit 304 Factory Sound YZ 125 2002-2021

Pro Circuit 304 Factory Sound

The Pro Circuit 304 Factory silencer is an absolute classic for all lovers of 2-stroke motocross bikes. It has been on the market for several decades and continues to be listed in the Pro Circuit catalog. Updated each year to fit the latest models, it maintains its status as a benchmark in this field.

Top quality and great sound

The 304 Factory Sound muffler lives up to its name - it produces the distinctive sound reminiscent of the factory bikes from bygone eras, sending shivers down your spine. In addition, Pro Circuit sets the highest standards for robustness and durability with this product.

• Brushed aluminum casing
• Connecting pipe and end cap made of 304 stainless steel
• Easily removable with 3 screws (for changing the insulation wool)

For Supercross fans, there is also the R-304 version, called "Shorty" - a shortened version of the 304, designed for SX and shorter race tracks.

Paired with a Works exhaust from Pro Circuit, you cannot only give your 2-stroke motocross bike a top-notch sound, but also achieve maximum performance.

Exhaust scooter, moped, motorcycle

The exhaust has a major influence on the performance of scooters and mopeds. By replacing the original with a tuning exhaust, you can improve the gas flow and increase the engine power.

exhaust parts

• The headpipe or header is the connection between cylinder and exhaust, and an exhaust gasket provides the necessary seal. In street-legal systems, the headpipe is equipped with a legally required restriction. Some people remove this restrictor to increase power.
• The actual exhaust body or expansion chamber is connected to the header pipe. In a classic 2-stroke expansion chamber type exhaust, gas pressure waves are used to improve engine performance.
• At the end there us the silencer or muffler that discharges the exhaust gases and, with the help of damping wool, also reduces the noise generated by the vehicle.

Replacing the exhaust

For 2-stroke engines, various settings and components usually need to be adjusted when the original exhaust is replaced with a tuning version. These changes include:

• Adjusting the carburetor by replacing the main jet.
• Upgrading the clutch or replacing the clutch springs.
• For scooters, it may be necessary to reduce the weight of the variator weights.

Tuning Level: Racing

We categorize our products into different performance levels  Original, Sport, Racing and High End , so that our customers can choose the right parts for their setup. It is really important to combine parts that belong to the same tuning level, this is especially true for cylinders, crankshafts and exhausts.

Racing products are designed for a more extreme uses and are developed primarily for racing. Whether you stay at 50cc or increase the displacement, the corresponding Racing parts produce much higher performance than the original parts in order to achieve maximum power.