The 2 attached documents I have got from JMC are leaked internal Yamaha UK memos to all dealerships and service workshops.

They show the range of the faulty ECU's up to frame number related, best thing to do is to check if your frame number falls within this range and if so print these 2 documents and take them to your dealer and they shall have no problem in sorting you out with a new ECU

The quality is not perfect but you can just about make out the frame numbers. Sorry but this was obtained by a mechanic and not officially from Yamaha.

For the benefit of all please note these are the affected frame numbers

XT660R Up to frame no. DM015-007858
XT660X Up to frame no. DM014-006257



And thanks very much to JMC for helping me with this even though now you are on the other side of the world, its great that you kept these things safe.