A couple of my machines were so gunked up that I wasn't sure what to do. They were dirty, rusty, seized and yucky. My DH brought in his PB Blaster (he has encountered some bad stuff in his former work as a GA mechanic) and it was what Skip had previously suggested to me. It took several applications over the period of a few days and on the appropriate parts I used a grill screen. My fingernails took a few days to get the black out but the machines look better and they work great. Just a note to the ladies, I found out that not dish-washing, food-handling or surgical gloves even triple layers don't protect the nails. Any suggestions from any of you to clean the nails after working on the machines? Nail brush and Dawn helps but the black color remained for several days.