Replaced mine with Boca Bearings (sealed). I believe sealed bearings are the way to go, especially if you take off and land anywhere that has potential for dirt and micro particles to get caught up in the rotor wash. Ever watch a helo in a movie with smoke around it? I also used an exacto knife to cut the plastic tabs off and release the motor. Easy taking old bearings out. I also replaced the washer with Teflon washers. You can easily damage the stock washers removing the motors so watch that if you plan on re-using them. Be VERY careful installing the new bearings! I used a little lube on seat to help slide the bearing into place. Do not pound on the bearing! Read somewhere someone put the bearings in the freezer for a while and warmed the motor (not in a microwave,,lol) slightly and said the bearings slipped in nicely as the tolerances were greater. Either way, the result is that SOLO flies smooth and much quitter than before. Best to have a spare motor on hand,,just in case. Good luck.
And you do have to take the motor off to replace both bearings.