No, there is no "burn in" period.
What gear did you have the tranny in? It is easiest to do what you are attempting with the tranny in the HIGHEST FORWARD GEAR. Is that what you were trying?
It's been over 20 years since I've worked on a "G", so I can't remember how the lined clutch disc is set up, but on most clutches, the center hub mechanism on the plate is offset, and if it is installed with the wrong side facing the flywheel, the center hub of the lined plate will contact the bolts holding the flywheel to the crankshaft, and the clutch will not release.