Harley Davidson Tattoos

What is good for cleaning boot leather off the pipes of my Harley?

You can not help it, God bless her heart. My wife rides on the back of my Harley with me everywhere, but she has a habit of always their boots against my heat pipes, and his leather boots she melts. After I called my tubes, use what I can to clean it with? If you asked me Easyoff use oven cleaner. Anyother tips?