I know I can't use a 530 O-ring or X-ring on my CB550 without trashing my engine case. Z1 didn't list a standard chain, so I sent him an inquiry. The answer is that RK (the chain manufacturer) produces two non-O/X-ring chains; standard duty & heavy duty. I'm looking into the dimensions to see if both will fit. However, I’m assuming the whopping 50 hp Honda claimed back in ’75 has degraded somewhat by now; and my guess is that any modern 530 chain will be overkill. Besides power transfer capacity (and assuming it fits…), what advantage would there be using the heavy-duty vs. standard duty? Longer life? Longer adjustment interval?