I'd tip him, those fit jobs are awesome and without his help/service you feel quite uncomfortable. I even tip mechanics for there services , even more so when they don't charge me.
I love walking into a shop, the mechanic eyes my bike, breifly looks it over notices something wrong. Then ask if he can see if for a sec, does a little twist here a little twist there, and somehow the bike feels even better, and more crisp than before. Then I'd ask how much do i owe, he grins and replies, it's on me. Those little jobs make such a difference, and sure enough im going to tip him.