I found out early its cool to make them whine with a tight belt but don't do it especially with the smaller long snout blower as the leverage the drive shaft has will actually bow the rotors and cause them to touch (no more blower) leave a bout a inch of slack, it will tighten when all the aluminum pulleys warm up, Have FUN!!
Front bearing are lubed from the front oil in the case they will last dang near forever (if the have gear oil), the rears are prelubed, if your too worried pull off the back cover and get a little grease in the bearing somehow, they generally are unshielded, I am use to 6-71's but most roots are very similar.