Polishing a crank is easy. Buy some 200 and 400 grit wet or dry sandpaper. Buy a little kerosene. Cut it(the sandpaper) into strips the width of the crank journal. Make damp with kerosene, wrap the paper around 1/2 of the journal and shine up the crank, starting with 200 grit. Don't spend much time in one place, but keep working your way around so the crank stays round and not egg shaped. After a few rounds/strips with the 200 grit, then rinse/wipe to remove all the grit and do the same thing over with 400 grit. If you're a purist, you can even go 600 grit, though it's harder to find.
The crank journal surface will literally get smoother and shinier as you go.
Speaking of roundness, you need either a micrometer that can measure two inches, or a decent dial caliper that reads down to a thousandth of an inch (0.001 inch) Prior to starting, you should confirm that your crank is round to start with. It should measure pretty close to 2.000" every way you measure it. If it's 1.995" in one axis, and 2.004 at 90 degrees to the first measurement, you've got problems. The idea is to start round and stay round. Judicious use of this fine grit paper shouldn't really cause much or any measurable change in the diameter of the journal, so don't go crazy. We're just knocking off the high spots microscopically.
Make sure you get all the grit out when you're done, as sandpaper abrasive is very efficient at killing bearings.
Good luck and have fun!
troy
