Because this gets asked a lot I thought I'd post the capacity for the different
Honda 250/350s per the Honda service manual.

CB/CL-250, 350 (175-185cc 5.9-6.3oz after draining) (195-205cc 6.6-6.9oz dry assembly)
CB/CL-250, 350K1 (175-205cc 5.9-6.9oz after draining) (195-205cc 6.6-6.9oz dry assembly)
CB/CL-250, 350K2 (175-205cc 5.9-6.9oz after draining) (195-205cc 6.6-6.9oz dry assembly)
CB/CL-250, 350K3 (175-205cc 5.9-6.9oz after draining) (195-205cc 6.6-6.9oz dry assembly)
CB-250, 350K4 (105-110cc 3.6-3.7oz after draining) (125-130cc 4.2-4.4oz dry assembly)
CL-350K4 (105-110cc 3.6-3.7oz after draining) (125-150cc 4.2-5.0oz dry assembly)
CB-350G (105-110cc 3.6-3.7oz after draining) (125-130cc 4.2-4.4oz dry assembly)
CL350K5 (105-110cc 3.6-3.7oz after draining) (125-130cc 4.2-4.4oz dry assembly)
SL350, SL350K1 (160-170cc 5.4-5.8oz after draining) (180-190cc 6.1-6.4oz dry assembly)
SL350K2 (160-170cc 5.4-5.8oz after draining) (180-190cc 6.1-6.4oz dry assembly)