I went to a big swap meet over the weekend and sold some parts bikes and picked up a '71 Sl350 and a '78 1/2 Rm 250. I'm kind of excited about the Sl I've wanted one for a while. i also got on the internet looking for solutions to clean rust out of the tank. Outboard motor guys have been doing it with a rod and battery charger. tape up the rod on one end and a plastic insulator at the filler cap, fill the tank with salt water and apply low battery voltage. One connection to the rod and the other to the tank. I'm trying it now, I'll let you know how it works.