Last year (2007), Honda announced discontinuance of the "F" and "K6-later" style pivot collar for the Fours. This leaves us with their earlier version, which lubes better if installed right, anyway. However, if you have a CB750 (late K5 or later "K", or any of the "F" types, your swingarm has one grease zerk in the center of the pivot that is, essentially, useless. The reason can be seen clearly in the picture below: the pivot collar on the right is the one from those arms. It has no grease spreading grooves, and neither does the associated swingarm bushings from Honda (never had any, just a "reservoir" in the middle). These arms usually seize the outer half of their bushings, for obvious reasons: no new grease will ever reach that area, no matter how hard you fill that center zerk. They last about 10,000 miles, then start tearing the bushings up.
If, however, you use the "K" pivot collar, and use an old swingarm bolt from an earlier "K" frame (with zerks and feed holes on both ends), you can easily fill both bushings from the ends. If you also grease the center zerk, so much the better. Add new bushings, especially bronze ones, and you'll likely never have to replace them again.
The left pivot collar here is Honda's original design, with a 3mm wide grease spreading groove. The center collar is a current (2008) model, modified with my Dremel tool, to have a similar-width spreading groove set (the stock ones are now only 1mm wide). This improves wear and performance, making for smooth, stickless corners with uneven frame loads (twisties). The one on the right, as I mentioned earlier, is just Honda's cheap, "last-ditch" design for limited-life, low-cost-to-build, bikes, toward the end of the 750's marketed life. The good news: you can make it BETTER than stock, with junkyard parts: get one of those double-zerk bolts and put it in your 750. You'll be glad you did.