How-To Tech: Rotax Power Valve Plumbing

The 125cc Rotax MAX EVO engine uses an Electronic Timed Exhaust Valve System.

With opening and closing triggered by the engine’s ECU, crankcase pressure is used to open the valve (for top end performance) and the spring external to the exhaust valve closes it (for bottom-end performance).

It is therefore important the various tubes are correctly installed for this to operate efficiently.

Derek Jones at Power Republic shows what goes where on a new EVO engine – applicable to Senior MAX, DD2 and the various TaG classes that run these engines.

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