Yesterday evening I finally got around to finishing off a wheel build for my road bike upgrade to 11 speed. I almost forgot to adjust the hub before putting the wheel back on the bike. I decided to open the (brand new) hub up to check how much grease was packed around the bearings, hardly any.... so I put some in quite successfully, then turned hub over, only to drop a bunch of bearings out the other side into a nearby tool box.... queue much swearing. I carefully tipped out the contents of my tool box, and finding only 2 of 3 bearings, but assuming I had them all, I put them back in and put it back together. Unbeknownst to me, another had rolled under a cabinet.
Packing it all up with grease, put the axel back on, forget to install the end cap, and mounted the wheel back on the bike. Only to realise I had forgot the end cap when tightening the QR skewer. Off it comes again, back on to the bike. Then too much play in the wheel, so off it comes AGAIN. Finally, I adjusted the cone perfectly. Back on the bike. Whilst cleaning up the tools strewn about the floor, I notice it, the other missing ball bearing. FFS, should have counted them all before putting it all back together... Had to strip it down and start again.
Note to future self, don't drop your ruddy ball bearings everywhere, and count them before sealing it up... GRRRR