left hand side as you sit on the seat perhaps ?
Might not be overheating, barrels being cast iron rust does get under the paint, it's job that needs doing from time to time unless you get them powder coated ( which some advice against).
I have a very thin flexible small diameter rat tail file that can strip off old paint between fins a treat, then coat with a heatproof paint,
Cylinder Black used to be the choice of many but lots of choice out there these days, it's a matter of personal choice I like shiny Black others prefer matt or satin finish