It's a mates tank off his K100, he's still cleaning it using a combination of soaking in methylated spirits and wiping with acetone. I soaked his pump in vinegar for 2 weeks, then methylated spirits. The pump seemed like it was jammed, on applying 12v tried reversing polarity still jammed. Even though it was jammed I didn't want to be responsible for totally destroying it. I gave it back to my mate and he applied higher voltage 18v alternating the polarity and it broke free. Out of 4 bricks only one has a usable fuel pump damper, which he is going to use with a new non OEM pump to get the K100 back on the road. You want to try getting the gunk off your hands, it took days, be warned wear gloves.
Regards Martin.