Upgrade intake performance with Boyesen 604 dual-stage motorcycle reeds, designed for select Yamaha two-stroke applications. These replacement reed petals are engineered to improve the response and efficiency of the engine’s intake system while maintaining dependable operation for trail, motocross, and recreational riding.
The Boyesen 604 reed design uses dual-stage construction to support faster opening and closing, improved low-pressure response, increased intake velocity, and greater flow area. This helps provide more responsive low-throttle performance and stronger overall engine breathing with a relatively minor component change. The reeds are also designed for extended service life, making them a practical replacement or performance upgrade for compatible machines.
Fitment includes the 1985 and 1986 Yamaha YTZ250 Tri-Z, along with the 1988 through 1992 Yamaha YZ125. Verify the year, model, and existing reed assembly before installation to ensure proper application. This product is manufactured by Boyesen and identified by manufacturer part number 604 and vendor part number 59-7604.
Boyesen dual-stage reeds are designed with a safety-focused construction that helps prevent engine damage if a reed breaks. Installation should be completed according to the motorcycle manufacturer’s service procedures, with all intake components inspected and properly sealed before operation.
Features:
- Dual-stage reed construction for improved intake control
- Faster opening and closing for responsive engine operation
- Improved low-pressure and low-throttle response
- Increased intake velocity and flow area
- Designed for longer overall service life
- Safety-focused design helps reduce the risk of engine damage if a reed breaks
- Fits 1985-1986 Yamaha YTZ250 Tri-Z and 1988-1992 Yamaha YZ125
- Brand: Boyesen
- Manufacturer part number: 604
- Vendor part number: 59-7604
Fitment:
1985 Yamaha YTZ250 Tri-Z
1986 Yamaha YTZ250 Tri-Z
1988 Yamaha YZ125
1989 Yamaha YZ125
1990 Yamaha YZ125
1991 Yamaha YZ125
1992 Yamaha YZ125