One can make some headway with this by using Alcohol and a plain white paper
towel...you can't get it all, but you can get a lot of it. Plan on using a
fair amount of towels. It will leave the wrap sort of patinated, but
intact. I have not tried this on leather yet...might I suggest turning the
bike upside down and work on a small out of site spot until you see the
results.
Tom Sanders
Lansing, Mi USA