Sorry to revive an old thread but this information was useful to me this last weekend. I took apart the linkage on my 2000 YZ250, and only the connecting rod bearings and the relay arm bearings had the "yellow cage" stuff. The swingarm bearings did not have the "cage", although those bearings are in a metal housing.
The bearings that had the "yellow cage" were mostly dry, although the bearings did not look worn. The yellow stuff must have some decent lube retention qualities, but I removed the stuff anyway. I'm guessing that as long as you give the linkage some attention once or twice a year, the yellow stuff is not needed.
Next time I lube the linkage, I'd like to replace the oil seals and bushings. Anyone know of a good replacement kit?