VHM High-Compression Cylinder Head Insert for Yamaha YZ65 – 6.80cc

The VHM AE32285-C 6.80cc cylinder head insert is an optional high-compression combustion chamber developed for the Yamaha YZ65 2-stroke platform.

Its lower combustion chamber volume increases compression compared with the standard VHM insert, producing a stronger low- and mid-range torque response. This gives the engine more immediate acceleration and a more pronounced pull when exiting corners, making it especially effective on deep sand tracks and other high-load riding conditions where maintaining momentum is critical.

The trade-off of this higher-compression configuration is reduced top-speed potential compared with a larger-volume insert. It is therefore best suited to riders looking for stronger bottom-end response and more usable torque rather than maximum over-rev.

The insert features a 6.80cc chamber volume, +1.25 mm piston height, and 0.80 mm squish, matched to a dome-style piston and Ø43.50 mm bore.

VHM’s interchangeable combustion chamber system allows the insert to be changed quickly without replacing the complete cylinder head, making it easy to adapt the engine setup for different tracks or performance requirements.

The AE32285-C is precision-designed for the VHM AA33174 cylinder head and features an engraved part-number reference for quick identification during servicing and engine tuning.

This insert is not compatible with the OEM cylinder head and must be used with the VHM AA33174 head.

Key Features

• 6.80cc high-compression chamber increases low- and mid-range torque
• Provides stronger acceleration and improved drive when exiting corners
• Particularly suited to deep sand tracks and high-load motocross conditions
• Quick-change VHM insert design allows easy adjustment of engine characteristics
• Precision engineered exclusively for use with the VHM AA33174 cylinder head

Technical Specifications