Only the PTO clutches used on the older model Cubs are considered to be, "rebuildable," but that does not mean the inspired person can't do it. But, on the newer clutches the clearances are so tight that if the bearing is bad, the components of the clutch likely rubbed up against one another which will make spending the time to repair the clutch a waste. Inspect it, and if anything rubbed it's best to just toss it in the trash.
I saw in the, "buy it now" section of E-Bay a whole slew of new Warner PTO clutches for Cubs, the most expesive one there was $239.00. Any time one of there clutches is removed or replaced on the engine it must be set to spec- don't try to do it by eyeball or feel, it must be set evenly with a feeler gauge. Set right they should last 20+ years, set wrong lucky to make it through one season. Too much belt tension can be a factor causing bearing wear.
-Fordlords-