VHM High-Compression Cylinder Head Insert for Yamaha YZ85 – 8.20cc

The VHM AE32286-C 8.20cc cylinder head insert is an optional high-compression combustion chamber developed for Yamaha YZ85 motorcycles equipped with the VHM AA33176 cylinder head.

Compared with the standard AE32286-E 8.40cc VHM insert, the smaller 8.20cc combustion chamber increases the compression ratio and shifts the engine character toward stronger low- and mid-range torque. This results in quicker acceleration, more immediate throttle response, and increased drive when exiting corners.

This torque-focused configuration is particularly well suited to deep sand tracks and other conditions where strong bottom-end response helps maintain momentum. The trade-off is reduced top-speed and over-rev potential compared with the standard or larger-volume chamber options.

The insert features an 8.20cc combustion chamber volume, +1.60 mm piston height, 1.30 mm squish, a dome piston crown profile, and a Ø47.50 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 compression and engine response to different track conditions.

The AE32286-C is precision-engineered for the VHM AA33176 cylinder head and features an engraved part-number reference for easy identification during servicing and engine setup.

This insert does not fit the OEM cylinder head and must be used with the VHM AA33176 head.

Key Features

• 8.20cc high-compression combustion chamber increases low- and mid-range torque
• Improves acceleration and delivers stronger engine response when exiting corners
• Ideal for deep sand tracks and traction-demanding motocross conditions
• Quick-change VHM insert design allows easy adjustment of engine characteristics
• Precision engineered exclusively for use with the VHM AA33176 cylinder head

Technical Specifications