Joined: Jan 2010
Posts: 9,797
Likes: 1,762
From: Northern California
Bikes: Cheltenham-Pedersen racer, Boulder F/S Paris-Roubaix, Varsity racer, '52 Christophe, '62 Continental, '92 Merckx, '75 Limongi, '76 Presto, '72 Gitane SC, '71 Schwinn SS, etc.
When I get to this point with the head of a dust cap, I take a tiny screwdriver and tap the handle with a small hammer as the tip digs into the plastic, then angle the screwdriver while tapping to rotate the cap out. Do this in a few places around the circumference of the plastic until it starts moving, but FIRST follow davester's advice and get a penetrant going to work in there.