Over the years since I began riding, which was in 1972, I have learned the following which all helps the sale, then of course, the use of sale funds to buy a different vintage bike! Because all of us here basically do that don't we?
Save all or get all paperwork you can for the bike you want to sell or even keep, in the long run, there is never too much vintage stuff to have With the bike! Especially Adverts and such. Documentation of repairs, or aftermarket goods.
Having or leaving the paint stock, as opposed to a NON standard colour INCREASES the value!
Leaving all the stock stickers and graphics, see above.
As all should know, aftermarket parts decrease the value, unless you have the stock parts and in reality, you should always change everything back to stock before attempting to sell the bike. UNLESS it is a HIGHLY modded bike with period parts!
Get the bike as clean as possible, even to the point of replacing parts before an attempt to sell. 300 dollars spent on new turn signal lenses, fenders that have no surface rust and all those little bits return MUCH more on a sale. As long as they are NOS or original parts.
try to not use repop parts unless they are quality repops then Never represent them as anything BUT a re manufactured or repop part. You will get busted by a savy buyer then you have a bad rep.
Detail the bike as well as it can be, never leave oil grime or anything on it for the pics of the sale or during a viewing. A little old oil residue can kill money off a sale.
Make sure the seat is in as good condition as possible, even with a repop cover, it has better resale value even if the paint has patina the seat should look excellent.
That is about it for now till I remember more, and of course make sure it runs perfectly!
this is all for those who want a good bike to look great, or a great one look flawless. Believe me, many over look even these things, or never think of them and therefore, don't make as much as they should on a vintage bike sale.
To tell the truth, I am glad my CB350F has patina because I am not going to sell it. I am going to ride it so would not ride it as much if it was perfect. Now if I were trying to sell it I would want it perfect and with about 500 clams could easily do that!