Hard, glass like, carbon deposits, heavy, dark brown to black carbon accumulations, some blocking almost the entire exhaust port. Severly scored cylinder walls from carbon particles breaking loose and being pulled down the cylinder below the piston ring. Stuck piston rings, heavily scored piston skirts. Rough bearings. Engines difficult to tune that have poor ring seals from thin oil ratios. Engines that "cold stick" easily from thin oil ratios poermitting the piston to heat up faster than the cylinder.