I have a WPS non o-ring 530H chain on my 75 CB550K. Doing some maintenance I popped the chain off and noticed some wear on the case plug/seal. Obviously this chain was just a #$%*hair too wide as it has worn the rubber off. Just wanted to give a heads up that apparently even some non o-ring types still need to be looked at. I am glad it didnt wear all the way through and guess I will add a higher quality STANDARD 530 chain to my list of winter goodies.