Originally Posted by yorkie_chris

OK here's a disclaimer... the closest I've been to working on a blade is stood 6 foot away from yours...

Anyway, the EXUP valve is a valve in the mid-pipe of the exhaust system, it closes at low revs and opens at high to give better midrange torque with a tuned engine.

You'll find hidden in the fairing somewhere a servo-motor with control cables which lead down to the exhaust valve, it wouldn't suprise me if a cable has got stuck or the exhaust valve is siezed. Is it lacking in power/midrange?