I would measure your 68 jet and see what’s that actually size of it and go down a lil bit to a 65 it looks like you are running a little bit to rich because of all that carbon build up on the spark plug, since it’s black build up and not white your running to rich but it looks like your close but not quit try 65 if ur running a 68 but remember every jet is different on how it’s measured so what ever your measure to I go down a little bit don’t go down a lot or you run in a lean condition