Motorcycle Repair: Under engine mounting bolt design difference, mounting bolt, cb77

Question

under engine support b   Hello Why are some engine under bolts just straight shanks and others turned down midway to a smaller diameter on CL72 and 77s ? My cl72 has the tapered middle section. I have a spare one that has no tapering of its midsection. The threads on the spare are in excellent shape so I was planning on using it once I install the oil pump . Would this create a problem by installing it? Was this possibly a cost saving device by Honda through less machine labor?

Answer
Bob, Honda went to great lengths to keep things light, but strong, in the beginning of production of many early models. My 1961 CB77 has hollow axles and turned down axle spacers, which were eliminated in later years, to expedite the manufacturing process. Many times the part number didn't change, if it was just a shift due to a production process change, rather than an actual change of critical dimensions. Not turning down the center of the bolt sped up the process of manufacturing the part. So, you are absolutely correct in your observation and assumption.

Bill Silver
www.vintagehonda.com