Thanks for the feedback guys, good to get the bearing size and code. I'll run it past my local bearing supply shop and see what the result is.
They have been supplying me with mostly cycle part bearings to date and are coming in at less than half the cost of Yamaha 'boxed' items. All these bearings are IKO or KOYO etc... so no cheap stuff!
I appreciate that there may be some items that are only available through Yamaha and I have no problem paying the asking price, but where I can source like for like and save in the process then count me in.
I'll let you know the outcome.
Cheers