Any Tricks to Removing Locked Fuel Cap?

Fixed it for you.
Didn't think there was a key. You need to buy better screwdrivers.
All you have to do is defeat the tumbler mechanism and you can open the cap. Of course you destroy that one in the process but it is free. Another trick to drill a small hole through the outer cap and run a screw or nail in until you hear the click. Turn to open, reuse cap with small hole in outer part.
 
imo do not use anything but dry lock grade lubricants. wd40 can help but once the job is done, flush it all out with brake clean. wd40 attacks dirt and damages the seals. been there, done that.
Understood although we are trying to get the lock open. He can worry about possible collateral damage after he gets the fuel cap open.
 
I don't know if this is going to be any help.
I bought a locking gas cap from Triumph to replace the original twist on/off.
This is the cap key next to the ignition key. Big difference in those.
 
Locking caps are also good for stopping people putting stuff INTO the tank..............