We recommend a 10W (light rider) to 15W (heavy rider) motorcycle fork oil. ATF is approximately 5W and replacing it with a heavier weight oil will stiffen up your front end.
Factory spec on the fork oil is of premium quality ATF (automatic transmission fluid).
CB450 / CL450 K0-K2: 290CC / 9.8 Oz. per leg
CB450 / CL450 K3-K4: 225CC / 7.6 Oz. per leg
CB450 K5 / CL450 K5-K6: 160cc / 5.4 Oz. per leg
CB450 K6-K7: 140cc / 4.7 Oz. per leg
CB500T: 140cc / 4.7 Oz. per leg