Walt, the rag's definitely a good idea-- I lost the teensy c-clip that holds the carb needle in place on that 71 CB100 as I was trying to put it back on 2 weeks ago-- finally found one left over from a 76 XL250 that was the same size.... but wow, was I hard on myself for trying that in my gravel driveway! --I should know better!!
On the 2300 driveshaft, perhaps a screwdiver, or maybe a piece of 1/8" steel with a u-shaped cutout --to fit around the u-joint, but bear on the c-clip-- might also work.