It's not necessarily rich. It could be lean. If the motor is cold with a Commander, you don't have warm up controls IIRC. On this 2 other bikes, did you change the exhaust and add a tuner? Still, they are different motors and the pipes you installed likely have a bit less back pressure at low speeds on the HD than on the other 2.

 

Too rich isn't good either. Unburnt gas will wash the oil from the cylinder walls, contaminate the oil supply and reduce the lubrication needed for the rings to live a long life.