"I've spoken to my friend about the bike. He said that cases like this are typically due to poor cabling by the guy who built the bike, and that it will be a persistent problem unless recabled. I checked out some local bike shops and they said it'd cost around $40 to fix. Thus, I unfortunately can offer no more than $80. I realize that this is quite a ways under what you were initially hoping for, so I don't expect you to immediately accept. My offer will stand for as long as you need it to, so if you decide to accept, ring me up and we can arrange a time for me to buy the bike."