We recommend a 10W (light rider) to 15W (heavy rider) motorcycle fork oil. Factory spec on the fork oil is of premium quality ATF (automatic transmission fluid). ATF is approximately 5W and replacing it with a heavier weight oil will stiffen up your front end.
CB500K: 160 cc (5. 4 ozs)
CB550K / CB550F: 165~170 cc (5. 6~5.8 ozs)