My 1994 Yamaha XJ600 Seca II was stolen a few years ago, and it was trashed when it was recovered. I’ve been gathering parts and, with the YZF-R1’s resurrection imminent, I’m in a position where I can (I hope) begin restoring the Seca. First step: Remove the seat.
But there’s a problem. The cylindrical seat lock is frozen. At least, I think it is. See, I only have one key. I’m pretty sure the one key I have is it. The other Yamaha key I have still has the plastic tube over it, and a tag, so I’m sure that’s for the YZF-R1. That bike is with the neighbour who is working on it. The Seca’s ignition block was not recovered, and the gas cap was destroyed removing it because its lock was frozen. So I have no other lock to try the one key in. I do have a set of a salvaged ignition block (ant triple-tree), gas cap, and seat lock, and I have had a pair of keys made (in addition to the one that came with them) to fit them.
I looked at the salvaged seat lock and cable, and it looked pretty straightforward. All I’d have to do is reach in with needle-nosed pliers and pull on the cable to release the seat. But Yamaha wisely, though inconveniently, enclosed the lock in a metal box that is part of the frame. I can’t feel the cable, so I assume it’s under the seat. (My Clymer repair manual isn’t helpful.)
There is one other thing that I cat try: remove the remaining Allen bolt holding the lock to the frame, and try pulling on it. Naturally, I’ve misplaced my metric Allen wrench set. 
Any ideas on what I can do to unfreeze the lock? The only thing I can think of would be to spray it with WD-40 and jiggle it.