Joined: Apr 2007
Posts: 820
Likes: 158
From: Ottawa, Canada
Bikes: Raleigh Classic 15, 84; Miyata 912, 85; Miyata Ridge Runner SE, 85; Miyata 610, 86; Miyata 100M, 86; Miyata Valley Runner, 88; Miyata Triple Cross, 89; GT Karakoram, 90; Miyata Elevation 300, 91; Marinoni Touring, 95; Long Haul Trucker, 2013
If it's really stuck, you might give it a little penetrating oil, wait a while, and then give it a solid whack.
You could also back out the cap screw a bit, and then tap (whack) that.