Okay I know the instant thought is a head gasket. There is no white smoke, machine is running well (when not fouling the right side cylinder, carb issue I think). There is no power loss. The coolant is very clean in the tank but the oil or sludge is building on the surface. I have a thought someone may have put oil in the coolant tank accidentally. Could this be the case or is it going to be a head gasket. Any thoughts or advice?
I would remove spark plugs and carefully examine the tops of the pistons with a maglight or a bend a light if you have one, if ingesting coolant it will wash the carbon off the piston top, this may be your mag cylinder where you say its fouling the plug. Something that happens to the srx over time is the white crusty build up and gets between the head and cylinder and causes leaks. The fix is usually to remove the heads and clean both surfaces, be sure o-ring groove is cleaned out, a small brass brush works well. clean with compressed air and then lightly spray with wd40 and install new o -rings.