if you've got another fork, IME, switching forks eliminates a lot of variables.
i know how frustrating this can be. i've spent a number of hours on one bike of mine ('79 trek 710, unwrecked with original fork) sorting out a hands free steering bias. turned out to be the narrow 20mm tires. the frame/fork geometry was so sensitive that when the 20mm tires wore out and i switched to 25mm tires, the problem vanished.
... at least that's my story, and i have no reason to not stick to it.
Last edited by hueyhoolihan; 05-17-14 at 02:43 PM.