Joined: Feb 2012
Posts: 19,290
Likes: 5,383
From: Rochester, NY
Bikes: Stewart S&S coupled sport tourer, Stewart Sunday light, Stewart Commuting, Stewart Touring, Co Motion Tandem, Stewart 3-Spd, Stewart Track, Fuji Finest, Mongoose Tomac ATB, GT Bravado ATB, JCP Folder, Stewart 650B ATB
It sounds like the centering sleeve/compression ring has been removed so the chance of rust developing between the upper headset cup and the steerer is strong, especially if one is steel and the other is AL. Penetrating oil placed on the exposed top section of the steerer might drip down and soften the corrosion/bond. More shock is the next step, and shock is sometimes more the issue then force is.
At some point the decision of what is more important to save comes into play. Is the fork worth more to you then the headset? Either can be destructively removed (grinding/slitting). Andy.