VHM High-Compression Cylinder Head Insert for Kawasaki KX85 – 7.80cc

The VHM AE32240-C 7.80cc cylinder head insert is an optional high-compression combustion chamber developed for Kawasaki KX85 2-stroke motorcycles equipped with the VHM AA33151 cylinder head.

Compared with the standard AE32240-E 8.00cc VHM insert, the smaller 7.80cc combustion chamber increases the compression ratio and shifts the engine character toward stronger low- and mid-range torque. This delivers quicker acceleration, more immediate throttle response, and increased drive when exiting corners.

This torque-focused configuration is especially effective on 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 configurations.

The insert features a 7.80cc combustion chamber volume, +1.70 mm piston height, 0.90 mm squish, a dome piston crown profile, and a Ø48.50 mm bore.

VHM’s interchangeable combustion chamber system allows the insert to be changed quickly without replacing the complete cylinder head, making it easier to adapt engine characteristics to different track conditions and performance requirements.

Because the AE32240-C increases compression, use of high-quality fuel with suitable detonation resistance is recommended.

The insert is precision-engineered for the VHM AA33151 cylinder head and features an engraved part-number reference for easy identification during servicing and engine tuning.

This insert is not compatible with the OEM cylinder head and must be used with the VHM AA33151 head.

Key Features

• 7.80cc 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
• Designed for use with high-quality fuel to help reduce the risk of detonation

Technical Specifications