I use a product called road rub, for the price its worth a try. Avalible at any HD dealer Good luck.

 

heat them up real hot then wipe off with a cotton cloth and a bit of honda spray polish , worked great for me on my chrome samsons not sure about the black

 

Oven cleaner works great, took it right off

 

Ex professional window washer from Boston. Using water with the #0000 steel wool will help to prevent scratching.

 

Steel wool usually does the job for me on my fatcat pipe i do it when the pipe is hot

 

Here's what worked for me:

Go for a ride to get the pipes good a hot. Soak a clean washrag with water and quickly wipe the area while the pipes are hot. Denote the word QUICKLY. I am not responsible for you getting burned, you have been warned.

This has worked on multiple occasions for me and for multiple material types that have come in contact with the pipes. I had some of my heated pants gear (more like snow pants) leave some melted plastic material on the pipes. Another time my wife had something on her boot heel before getting on and left a white milky melted stain.

All that was left was really nice Chrome pipe and not even a scratch. Your mileage may vary. But it was a lot cheaper (free) and no serious chemicals were used in the process so it's a no brainer for me.