Caveat: I've done the research, ordered up the bearings, ordered up the bearing tool I reference, but not done the actual replacement yet. I'll update this posting if my research proves either to be wrong or right! --- If you notice that you've got a motor that sounds harsh when it runs, the odds are the bearings need replacing. When that happens, based on the research I've done (with the great customer service I got from Gareth Burrows of Boca Bearings -- you can reach him at firstname.lastname@example.org, web http://www.bocabearings.com), here's the kit that you need to order to replace the bearings with top quality ceramic sealed bearings: kit #BMK-080C-OS: http://www.bocabearings.com/bearing-inventory/Radial-Bearings/21490/xx-BMK080COS This kit consists of two SMR694C-2OS #7 NB2 bearings that are ceramic, high-end, bearings designed for a dusty environment. Bart, the administrator over at multirotorforums.com has developed a neat hand tool to swap out bearings without even having to unplug the motor wires: http://www.multirotorforums.com/showthread.php?6648-Motor-Bearing-Press-Tool . He's also done an excellent video showing you how to use the tool at . You can order the tool by sending a Paypal payment to Bart at email@example.com for $24.50. You'll get the bearing replacement tool, some replacement washers and spring clips. Andy.