KTM/Husqvarna TBI Exhaust Valve Expansion Cap (24-25)

This larger volume exhaust valve cover for TBI engines (KTM/ Husqvarna and GasGas) was developed to improve engine performance in situations where it is most used: low RPMs and small throttle openings.

Its action is especially effective before the exhaust valve is fully open, providing a more consistent, progressive, and controllable power delivery. Between approximately 3000 and 5000 rpm, and at partial accelerations, the engine shows a fuller response and a clear feeling of more available torque, facilitating control in technical riding.

This behaviour makes the product particularly suitable for trail and hard enduro, where traction, predictability, and smooth power delivery are crucial for performance and for reducing rider fatigue.

How it Works

In 2-stroke engines, pressure waves generated in the exhaust system help increase power at high RPMs but can hinder efficient cylinder filling at lower RPMs. This effect ultimately penalizes the engine's torque and response in the RPM ranges most used in technical riding.

The larger volume exhaust valve cover introduces an additional chamber that acts precisely in these conditions. When the valve is still closed or in the initial opening phase, part of the pressure waves are smoothed within this chamber, reducing their negative interference with the gas flow.

The result is a more effective cylinder filling at low and medium RPMs, translating into a more immediate throttle response, greater control, and more usable power delivery from early on.

After a development process based on practical tests and careful tuning of the internal volume, a solution was achieved that provides consistent and measurable gains in the low and medium RPM range, significantly improving engine behaviour where it really matters.

Compatibility

Compatible with 250 cc and 300 cc TBI motorcycles from the following brands:

• KTM
• Husqvarna
• GasGas

For 2024 and 2025 models only