OKAY KIDS, for those of you that are new to moto-maintenance.........
"On a rear-stand, run the engine at an idle for ten to fifteen minutes in first gear to warm the chain".......do not insert rags, towels, or fingers "ANYWHERE" near rear sprocket / chain link engagement area. "Shut off engine, and finish cleaning duties and lubricating duties by rolling rear tire "by hand", ENGINE OFF. When finished, start engine and test ride.
"For those "without" a rear stand, ride moto for ten to fifteen minutes to warm chain, turn engine off, put bike in neutral, clean a section of drivechain, move bike forward or rearward cleaning a section and lubing a section of chain until entire chain is clean and lubed. Start engine and test ride.
Simple enough once done. Second time is easier. Sorry to address this in kindegarten terms, but the pic of the dude in the emergency room lost fingertips. THIS COULD BE YOU.
For the rest of the moto-folks, I slammed my fingers in a car door when I was in second grade. My fingertips looked alot like the guy's in the pics.....hurt like H3LL.......I've NEVER caught anything, anywhere since. For those that can do it, "do it", for those that have never done chain maintenance, "don't try it" (look at pics above, once again). "THEN, do it by hand / ENGINE OFF".