I used a 50/50 mix of acetone and ATF fluid, set it on fire outside, and let it burn for a couple hours. Finally I decided to quit messing around and I pulled the motor and did the old fire in the barrel trick. I put a mix of acetone and ATF in the plug hole, rocked the bike back and forth in 4th gear, trying to get it to break free.
Every day for a week I would heat the barrel up with a propane torch and tap on it with a brass hammer. This spring I brought the bike over to my shop at work (I'm a mechanic at a golf course) and set to getting the motor freed up.
I poured some Marvel Mystery Oil down the plug hole and it sat in my garage for another two years. The motor was locked up, rings rusted to the cylinder wall. Fine by me, I had no urge to sell it anyway! It came with a Mikuni carb on it, Preston Petty fenders, and Redwing rear Shocks.
He knew I was into British bikes so he gave me the BSA but told me never to sell it. Two years ago I was lucky enough to have a family friend give me his old BSA B50 he used to race back in the 70's, but had been sitting in his shed ever since.
