Many years ago, used a chemical paint stripper designed to remove paint form aircraft purchased from an auto parts store. Many not be able to buy anything that strong any more. If I would do it now, would take it somewhere and have some sort of media blaster remove the paint.
Keith, if you’re going to get it powder coated, they’ll have to sandblast it anyway. Talk to the powder coat guy and ask if he can blast the frame or send to where they have it done…
BTW Plug here, Anthony Bros. in New your do a great job on powder coating and are very reasonable…..
If you want to see the original metal surfaces/ weld HAZ then you probably want to avoid media blasting and also avoid using anything besides white scotchbrite to loosen the coating. (yes, this will be frustrating) Also might be a good idea to throw down some good 2-part clearcoat once you get the frame cleaned off so the steel doesn’t rust too quickly.
Mar-Hyde Tal-Strip II Aircraft Coating Remover is the best stuff you’ll find for stripping paint from a kart frame if you can find it. I used to buy it from Kragen Auto Parts. May not be able to get it from an auto parts store these days… it is nasty stuff! Aircraft Spruce might be a source.
The aerosol can version is fantastic but be very careful to use in a well ventilated area with no breeze and wear gloves and clothing that cover all skin. I used the stuff to strip a Tony chassis and it lifted the factory coating off with ease.