RE: DL-50 engine
That plug doesn't look lean, it looks pretty close to maybe a little rich. The grey color makes it a little difficult to read accurately in just a photograph, some fuel additives give plugs that color but so does detonation. Before making a definitive call I would like to know what oil you're using,how you go about adjusting your carb, what your needle settings are,and your altitude. Super8 posted some great information on tuning.