4 ought (0000) steel wool and kerosene. But the rust will just come back. Better bet is to sand the pipe and spray with a high heat paint, or buy some Cermachrome paste and follow the directions. Order the paste from Speedway motors, Jegs, Summit Racing, or such.

Savage headpipe is a perfect example of cut-rate modern manufacturing practices...
-WD

Personally, I'd use some naval jelly to remove the current rust, then sand it to rough the surface, and paint it flat black with high-temp paint.

Rust "remover" paste. It neutralizes the rust particles. Then you can sand the pipe and spray it with AT LEAST 2000 degree paint. I tried 1200 degree on the tailpipe, and following the can directions to the letter, the paint blistered and fell off. So next time I decide to try and improve the pipe's look, I'm ordering Cermachrome paste. 2400 degree ceramic/stainless paste that cures like the Jet-Hot professional header coating.
-WD