Some of the calls and messages that come my way are about minutiae of the smallest details of the older models. Forums are rife with conversations about whether or not the carburetors on the Super Hawks and Scramblers had little drain hoses hanging off the bottoms of the float bowls or not, for instance. In the same vein, there is confusion about where the air vent hoses connect to on the air filters or if they connect to anything at all.
A recent questioner attached an image from the factory Honda CB72-77 Super Hawk parts book showing a drain hose attached to the float bowl on the left side carburetor. What appeared to be substantiation of the fact that a drain hose should be attached to his carburetors for judging purposes raised the question again which needed confirmation.
Fortunately, the Bill library has a number of first-edition parts books, which come in handy for answering questions such as these. Using the 1961 CB72-77 parts book for a starting point, the images did not show any drain hoses. Referencing the OEM Honda ID book images, which were received from AHMC back in 2000 for inclusion into the first Vintage Honda Buyer’s Guide book published then by MBI (Motorbooks, International), the side profile of an early CB77 clearly shows NO hoses hanging off the carburetor float bowls. So how did images of carburetors with float bowl hoses show up in later editions of the parts books?
Reviewing the “left side” carburetor images in the “world version” CB72-77 parts book, published in 1969 showed the same curious drawing of the carburetor with a float bowl hose, but as the details were more carefully studied, it became apparent that the drawing came from another Honda model and was transferred over to the Super Hawk parts book, intact. Curiously, when the “right side” carburetor drawing was viewed, there was no drain hose shown. Small wonder that there is such confusion over this particular question!
The left side carburetor drawing included “power jet” features which were used on the CB72s only, but the image seemed to be taken from another book in the library; the 1962 CL72 Scrambler parts book! The features of the power jet carburetor bodies are seen on the CL72 carburetors, however all the functions are disabled. The little cover at the top of the carburetor body, which normally holds one of the fuel/air corrector jets, usually holds a non-functioning spare main jet instead. None of the air correction fuel pickup tubes, used on the CB72s, are present in any CL72 carburetors. Honda chose to use the CB72 carburetor bodies, but deleted the power jet functions, opting to just enlarge the main jet sizes to compensate for the deleted system function.
More intriguing is that the early drawings show “round bowl” carburetors, which did not have drain screws, but did obviously have overflow tubes in the float bowls. The fittings for the overflow tubes are entirely omitted in some of the early parts books drawings. Additionally, the very earliest 1962 CL72 Scramblers had round bowl carburetors, but then these were changed mid-production to the square bowl varieties, which were not seen on the CB72-77s until about 1964.
In the last 1969 CB72-77 parts book, the image page of the left carburetor appears to show an intact square bowl carburetor, while the exploded parts drawings indicate a round bowl carburetor. Both square and round bowl carburetor parts are listed; however there is no clear indication about when the changeover took place. It is interesting that this last published parts list, which seems to encompass 250 and 305 versions, do not even show the drawings of the power jets or list the power jet part numbers.
The general view, based upon many years of experiencing all forms of 250-305s, is that the “square bowl” carburetors showed up on 1964-later models. The last three 1963 CB77s which have gone through the shop all had “round bowl” carburetors fitted.
The 1962 CL72 parts book shows the overflow tubing drawn away from the end of the fitting, but the parts listing for that tube has it as a “pipe, power jet” part number vs. the 16235-259-000 pipe, overflow part number used on the CA72-77 models. Later-edition CL72 parts books continue to show the hose, just away from the overflow fitting, but do not reference a part number to it. So, the best guess is that whoever was drawing the carburetors for the CL/CB72-77s had seen the CA72-77 Dream carburetor illustrations, which do have an overflow tube attached to the float bowls and just transferred that part of the image over to the newer models. Remember that the wet-sump 250-305 Dreams were first out of the gate in 1960, with the CBs following in 1961 and CLs showing up in 1962. So, images already done for the Dreams apparently were reused on the early parts lists for the Super Hawks and Scramblers.
If you consider the huge number of products flowing out of Honda’s factories in the early years, the number of people required to engineer, create the drawings and specifications which eventually lead to production of parts and finished products was enormous. Hiring talented young people in post-WWII Japan must have been a daunting task and certainly there were probably a few “slackers” in the bunch. Or, perhaps, those who drew the parts really didn’t understand the function or design details of the part they were re-creating for the parts and service books. They were just artists who had a talent for imaging the parts that someone probably laid on their work table and were told, “Draw this!”
With the untold masses of jobs to do in the creation of parts books, service manuals, advertising fliers and other graphic endeavors, there were bound to be some mis-steps in the processes. While the vast majority of materials were probably produced in Japan, even American Honda has had an “oops!” moment from time to time. When AHMC announced the new CL77 Honda 305 Scrambler in a full-page magazine advertisement, the close-up of the engine revealed 247cc on the cylinder base! Someone didn’t check the details properly and reused the 250cc CL72 factory photos instead.
The take-away is “Don’t believe everything you read or see in print,” as even the factories can and do make mistakes. Sometimes it takes a village to come to a consensus about a particular issue like float bowl overflow tubes; or you can ask Bill!