While performing post break-in maintenance after top end work on my 1971 Roadster (cylinders honed, new rings, new valves, head gasket, etc.) I noticed ugly deposits on the tops of the pistons. More pronounced on left side but some on right as well. Does anyone have ideas of what would cause this and what to do about it? For the last 100 miles I have been running Sunoco 260 GTX Unleaded 98 octane fuel. Carbs are standard Amal concentrics. The bike has been running great. Starts first kick cold & hot, idles smooth at 1000rpm. Good performance through the throttle twist. I provide pictures below: 2 photos of the left piston: then 2 of the right piston: Then this is what they looked like approximately 100 miles before: Then a picture of how the plugs look now: Any help is appreciated.