SJX426 

When I commuted to work, I parked next to a guy with a Langster. He was tall and his post was short. Frozen in place. The post head had come loose and rotated so he had to make sure the saddle nose point straight ahead!
I brought a can of KROIL and would apply every couple of days for, idk, a month or more. Never came loose.

He parked it, locked to his railing one weekend, forgetting to bring it into his apartment (Washington DC). Sunday morning the cockpit was gone and the wheels. He was really upset with the whole thing and mentioned that he was going to sell it on CL. I said " let me know before you post, I might be interested." Two weeks later he offerred the remains for $100 but wanted to keep the brake calipers. I countered with $50 because of the stuck post. He agreed.

Many hours after attempting many of the mechanical solutions mentioned above, I resorted to lye. I know this is Al with steel post. There wasn't much post left at the end. There was about 12" of stuck post.