I have had very good luck powder coating Yamaha A arms. The trick is heat absorbant paste. First clean and totaly degrease the arm and ball joint. Then take aluminum foil and make a cone or funnel around the ball joint. You can use safety wire and wrap around the ball joint in the same grove the stock clip uses. Once you have the cone built you need to pack it with the paste, maybe 1/2 ounce per ball joint. Don't overbake I have coated arms with both single and double stage powders and havn't melted a bushing yet. The paste I use is something like Thermopaste I get it at a local HVAC supply company. Be sure that you leave the arm upright when curing it other wise the paste will try to melt out. Good luck and don't settle for non coated a arms its very possible.