A little while ago I did some research to find out the size, type and nomenclature of the various front and rear wheel bearings. With the invaluable help and cooperation of a UK bike bearing supplier. I can now offer this list for your future reference. Many thanks to Marc for all his help in putting this list together and confirming the details are correct.
UK/European owners might like to note that Marc supplies complete kits of the bearings you need and at very competitive prices.
You'll see that the list also includes the type and sizes of taper roller steering head bearings should you wish to change those.
Front Wheel Bearings & Seals (BikeBearings UK kit YA004)
Rear Wheel Bearings & Seal (BikeBearings UK kit YA001)
Sprocket Carrier Bearing & Seal (BikeBearings UK kit YA002)
Tapered Steering Head Bearings (BikeBearings UK kit YA003)
I hope you find this useful and that it saves you time and expense buying replacement bearings at inflated Yamaha dealer prices.