Hello Fellows,
In reference to parts suggested to be "Original" to Early & Late Production sandcast machines:
Regaurding horns, to date, i have contacted 5 individual members owning VIN's 175 to 325. These 5 machines APPEAR to all have original horn from date of manufacture, early 1969.
I would like to thank these 5 members, i would not be able to share this information without their help.
Citing the following as examples to support this statement: "Factory Parts Manuals should not be relied on as sole source of reference to determine what part is or is not "original" to bike."
A number of cases can be noted in Parts Manuals where actual part number does not change when the acutal part changes or part number does not indicate a change in part was made.
Seats for example -
1. Per 69.7 Parts Manual, pn is 77200-300-020A.
2. Per, 1st Ed., Parts Manual, published February, 1971, CB750-CB750K1 - same part number (77200-300-020A) used for seat on machines CB750-1000001 - 44649
It is known 2 variants of seat pans exist. Early Production seat pans had fewer holes in the metal base than Late Production seat pans. Unknown (to me) at what VIN seat pan with fewer holes was changed to more holes.
Other examples of same part number used on actual different parts include, upper brake hoses, RH kill starter/kill switches, fork top bridges & oil lines. These parts all share same part number, Early Production machines used a different part than Late Production machines. (unknown to me at Exactly what VIN these parts changes occured.)
Going back to horn topic:
Appears 3 different types of Left Hand horns exist:
1. Gray plastic body horn w/ gray wire sheath.
2. Black plastic body w/ gray wire sheath
3. Black plastic body with black wire sheath
Horns "original" to date of motorcycle manufacture all appear to have numbers stamped in plastic; numbers not printed in ink ("inked" print horns are later date of manufacture & OEM Honda replacement part, not "original" to date of manufacture.)
Gray plastic body horns are pictured on Early Production bikes, in numerous magazine articles and Factory literature. It is ASSUMED these Gray body horns could have been used on VIN's before 175 and PERHAPS not afterwards.
All 5 machines from VIN 175 to 325 have a black plastic body horn with black wire sheath. It is known VIN 1292 has a gray body horn with a gray wire sheath. (To date, on a motorcycle, have not noted a LH black plastic body horn with gray sheath.)
It is also known, "Running Production Changes" were implemented on the Factory Assembly Line. That is, various parts from other models such as the 305, 350 & 450 were used on the 750 during Early Production run. It is known, 305, 350 & 450 models used gray plastic body horns.
Referencing the above Parts Manuals for horn part numbers, 2 pn's are noted; 38100-300-013 & 38100-300-023. The K1 Parts Manual indicates the "013" horn used to VIN CB750-1003950 & the "023" horn used beginning at CB750-1003951. It is ASSUMED the change in pn SUGGESTS a shwitch from LH mount horn to RH mount horn. Frame number 50100-300-050B supports this statement, as this pn is used from CB750-1000001 through CB750-1003950. Part number 50100-300-060B is used beginning at VIN CB750-1003951.
To date, i have not found (yet) evidence to support horn parts numbers suggest a gray or a black wire sheath.
Finally, i am not aware any PRODUCTION LH mount horn or frame used anything but a flat bracket to mount horn to frame. Again, this is an example of where the Parts Manuals are not reliable as a sole source of reference. The 7.69 & the K1Parts Manuals both indicate a mounting bracket that has two 90 degree bends, NOT a flat bracket as found on Early Production machines.
To date, i am not aware (yet) of any Production LH mount horn using this "double bend" bracket. It is also known Honda Factory literature, such as Owner's Manuals & Factory Repair Manuals used photographs to DEPICT a concept. And, these photgraphs used to depict a concept frequently were pictures of Early & Late Pre-Production machines.
In closing, i appreciate the debate brought about by the "horn advertised recently on Ebay." There is only one piece of evidence to possibly suggest this horn not to be a correct and/or original horn. The horns on the 5 machines noted above all have the green wire on the bottom and black wire on top. The horn recently on advertised on Ebay has the black wire on bottom & green wire on top. Other than not having a mount bracket, the horn on Ebay, fits all tests proposed within this email, to be accepted as an "original" and/or "correct" horn.
Finally, i do not consider myself an authority or an expert. I will state i know more than most and not as much as some. My research, assumptions and theories on horns (or any other parts) are most welcome to debate. I don't mind being "taken to school." Sometimes, there's no better way to learn.
There are a number of minor details (some not mentioned in this email) on Early & Late Production sandcast bikes that can be argued whether or not are "original" or "correct" for the Early Production machines. I am not aware, with 100% accuracy, a global statement can be made, citing one single reference (such as the Parts Manual) that would say with absolute authority a particular part is "original" or "correct."
What fun !
Steve Swan