Watch e-Bay... I've seen mint-condition, early CB750's go for $3k+. It is just crazy, sometimes. Other times, the bidding never takes off.
If you list it on e-Bay, make sure you take 6+ photo's, and pay e-Bay to feature them in your ad -- the more photo's, the better. Keep an eye on how much your ad will cost you, for all of the photo's. Put in a
reserve price of the
absolute minimum you are willing to accept, and put your
starting price no more than $500 below that, or you may run into bids that never meet your reserve price. Make certain to point out any/all flaws in your bikes, in the text of the ads. Take photo's of the defects, up close, so that bidders can't claim you deceived them, later. Be careful on how you take payment -- cash is always the best!
Spend the time to learn e-Bay's policies, before you list... Afterwards, it will be too late, and you may have handed someone enough rope to hang you with. Selling them on e-Bay is likely your best option, for maximizing your cash-out, as you will reach a m-u-c-h larger audience, with deeper pockets. There may have been hundreds of thousands of these bikes imported into the US of A, but very few are in near-mint condition, or better. Cheers!
1979 CB750K (sold, 2012, but not forgotten)
1983 Kawasaki 440 LTD Belt Drive (sold, 2011)
1993 Kawasaki Voyager XII