Hi,
There are definitely trademark issues with this name. USPTO.gov shows many TMs with these words going back further than this domains 2001 registration. Harley is also a very well known brand going back to the early 20th century. Harley's TM holder did not have to lay claim to this domain to have rights to it as those rights preexist in the TMs. They can wait as long as they need to before filing a claim for it with the UDRP.
It's a difficult choice to make but I can tell you this much. If you release it, someone else will pick it up and try to sell it and run the same risks. If you try to hand it over to them they can still fight you. It's a no win situation.
Do your best to release it without further violating their TM rights. This will benefit you more than money ever could. How? By keeping your name out of a UDRP suit. They would spend $3-5k to fill it. This suit, which they can easily win would end up posted on many Law websites for a long time, with your name all over it. It also can be used as reference against you in future domain disputes, therefore damaging your reputation.
I apologize for making this appear so damning but it is all very true.