Was happily thrashing round Cadwell on my MC21SE and it suddenly wouldn't rev over 9ish-K (after 2 or 3 sessions). Got back to the pits and sussed that the powervalves had ceased to function.

Have tried another powervalve servo/motor which has not worked - tried this as the old servo was tested and I was told that 'the motor has bad commutation and the potentiometer is not changing linearly over the whole scale', so I decided it is probably shot.

Has anyone any suggestions on reasons for this and/or ways of trying to find/remedy this please? Summer is here (apparently) and want to try and make the most of what is left!!

Thanks