Cylinder Works 05-21 Yamaha YZ 125 125cc Standard Bore Cylinder Head

This is a standard bore cylinder head from Cylinder Works for your 2005-2021 Yamaha YZ 125. It's built as an OEM-style replacement, meaning it's made to fit and function like the original part, but with some performance improvements. It comes with cam caps and bolts, so you can get it installed right away.

The combustion chamber is unshrouded, which helps improve airflow into the engine. It also features a blended bowl and a competition-grade valve job, which means the ports where the air and fuel mixture enters and exits the cylinder are smoothed and shaped for better performance. The valve guides are shortened to work with high-lift cams, giving you more torque and power. Plus, it uses C630 nickel/aluminum valve seats and guides, which are tougher on the valve itself, helping to reduce wear over time.

Keep in mind that the valves, springs, retainers, and lifters are sold separately, so you'll need to pick those up to complete the assembly. The ports are shaped like the stock ones, but they're designed to deliver higher performance than the original.