This help file should help show why you may think you are unable to add the full 80 characters for your eBay title.
eBay will restrict you to 80 characters, although you may think that you have under 80 characters there may be some hidden characters that you are unaware of. An example of this is the & character, when uploaded into the system the character will actually be uploaded as, &, so although you will only see the & symbol displayed, there will actually be an extra three characters in the background. If you are using any special characters like this try removing some spaces or rewording your title to fit everything in.
If you have tried this and still believe that you have less than 80 characters but are unable to add any more on your title please get in contact with our support team via email at firstname.lastname@example.org and they can investigate that for you.