What Does a "B" Mean in Harley VIN?

[Tommo]

I was hoping someone would have a definitive answer to this question as it has troubled me for a number of years and although I suspect I have an answer to it I must emphasize that I have no proof what-so-ever as to the statement I'm going to make a bit further on.

Firstly we need to break down the letters before the numbers.

J = Generator or Electric model
D = 3 7/16 bore / 9.5 h.p. / 74 cu in motor
CA = Aluminium pistons
CB = Iron Alloy pistons
No CA or CB = Cast Iron Pistons

The best place to find this information for 1924 models is on page 3 of the 1921 to 1925 Spare Parts book issued on the 1st September 1925.
It's no good going to the 1920 to 1924 Parts book or the 1922 to 1926 Parts book because the information in each of these is not exact enough to answer the questions raised here.
It's really important to follow things through year by year in the parts books when making decisions on subjects like this and in doing so you will find there are numerous things that only appear in one years Parts book.

Now to the "B" following the numerals. In 1924 several mods occurred that would be of concern to someone working on these motors with the major one being an alteration of the balance factor due to the flywheels being changed from spoked to solid. As far as I can find out there were 1924 models with both styles of flywheel assemblies so there needed to be some way of identifying what style of flywheel assembly was in what motor so maybe that is why the "B" is there.
Searches of the "Shop Dope" releases by myself and several other J model nuts have failed to find any mention of this so it must remain just a theory and is not proven in any way.

Also for 1924 you had the option of a Zenith carb and it has been suggested by others that maybe the last letter signified that the bike was a special order machine that was fitted with optional parts that were different to the standard production model.

Until someone finds that elusive bit of paper with the key to the factory code for letters following the numerals I feel that we just have to take an educated guess as to what exactly these letters mean.

I'm going to emphasize here again that I have no proof what-so-ever as to the statement above and everybody please put your thoughts up here so we can try and solve the puzzle

Buzz I hope this helps.

[HarleyCreation]

I was hoping someone would have a definitive answer to this question as it has troubled me for a number of years ...

(snip)

Now to the "B" following the numerals. In 1924 several mods occurred that would be of concern to someone working on these motors with the major one being an alteration of the balance factor due to the flywheels being changed from spoked to solid. As far as I can find out there were 1924 models with both styles of flywheel assemblies so there needed to be some way of identifying what style of flywheel assembly was in what motor so maybe that is why the "B" is there.

Searches of the "Shop Dope" releases by myself and several other J model nuts have failed to find any mention of this so it must remain just a theory and is not proven in any way.

(snip)

Until someone finds that elusive bit of paper with the key to the factory code for letters following the numerals I feel that we just have to take an educated guess as to what exactly these letters mean.

Why guess when we have that "elusive bit of paper" in the 1924 Factory layout sheet? This was their internal method of keeping track of models and contains much more than the parts books do, including entire models that seem to be special order only to a favored few (or those who hollered loud enough).

Four models are listed with a "B" suffix at the END of the serial number. Next to each model description with the "B" suffix is clearly typed in: "Iron Alloy Pistons." Only models with the "B" suffix say that. The correlation is 100%. But it's only for that year. A detail that apparently escaped getting into the parts books.

Hope this helps.

PS: I would only add that Harley's system of numerology and letterology is filled with contradictions and exceptions. It is NOT entirely consistent but contains all sorts of tacked on additions, repetitions, and Kabbalistic-like confusions. No doubt too much beer drinking on the job and over the lunch hour...

[Tommo]

Herb
I wasn't aware that such a record existed and because there is a 1924 FDCA here in NZ with a B suffix it was assumed that this bike would have left the factory with aluminium pistons as per the CA and not Iron alloy as per signified by the B suffix. Very confusing.
If possible I would like a copy of that particular piece of information to add to my archive.

[pete reeves]

There most be a reason why the cases are stamped with CA.
Could it be that some 24JDCA motors had the pistons changed to iron after the cases were stamped with the CA?
Or could they have been stamped with the CA by mistake?
It is my understanding that the factory would change the crankcases if there was a problem with the Number, So over stamping the A would not have been an option. Adding the B to the end of the number would identify what spec the motor was with out ruining the VIN and therefor would not involve a change of crankcases.

Pete Reeves 860

[Tommo]

Bill, 23JDCA 808
Could you look and see if there any sign of a B stamped on either of the cylinder base flanges of your bike. If they're there they should be on the left hand side.

[Chris Haynes]

I would only add that Harley's system of numerology and letterology is filled with contradictions and exceptions. It is NOT entirely consistent but contains all sorts of tacked on additions, repetitions, and Kabbalistic-like confusions. No doubt too much beer drinking on the job and over the lunch hour...

The MoCo did have hourly beer rations in the workplace. John Nowak presented Bruce Palmer with his genuine H-D embossed tin beer ration cup.

[Chris Haynes]

I have factory photos of a 1924 with an X at the end of the number. Any guess what that is?

[Rooster]

I have factory photos of a 1924 with an X at the end of the number. Any guess what that is?

"Experimental"?

[23JDCA 808]

Bill, 23JDCA 808
Could you look and see if there any sign of a B stamped on either of the cylinder base flanges of your bike. If they're there they should be on the left hand side.

Hi Peter. No sign of a B on either cylinder base flange edge, on the left side. ...bill

[Buzz Kanter]

Here is a closeup photo of the VIN on my 1924 JDCA. Sure looks factory original to me.


And no signs of a B in my cylinders either.

[Tommo]

I found it very hard to believe that the factory would stamp the engine number twice with letters to describe the same thing, no matter how many beers someone had it just didn't make sense, so I spent some time ringing my HD contacts both here in NZ and in Australia to see if I could get some sort of answer.
An ex HD mechanic who started work at Jones Brothers, the NZ importers, at 14 years of age and is now well into his 90's told me that I should be ashamed for not knowing the answer and that I could find it in some of the HD "Service Dept. Bulletins" he had given me years ago.
As he likes to keep you guessing it took some gentle persuasion for him to finally reveal the following over the phone.
A = Police motor/ motorcycle
B = High compression cylinders fitted
E = Fast motor
I knew about the E motors but couldn't remember anything about the other two so went looking for the Service Bulletin and finally found it.
"No 90 dated Feb 25th 1921" and it describes all the above mentioned letters but states as per the B letter motors that quote "This model is no longer being built"
Back on the phone to Ern and all I got was bull**** those motors came to NZ right up until 1924 and if you want one to go real good now go looking for a pair of cylinders stamped on the flange with a B.
This led to me asking both Buzz and Bill if they could see if their cylinders were stamped with B thus at least going some way towards proving this theory.
Sadly neither are but another HD nut in Auckland does have a rear cylinder that is stamped B on the base flange and I have a front that has a 5 stamped there.
Both these cylinders are for the early stud pattern and are what we call "small base cylinders" here in NZ.
Before any of us can definately say this is the answer I would like Herb to carefully read the document he quoted to see if anything in it's wording can give credence to this theory. Meanwhile I'm trying desperatly to contact the owner of 24FDCA****B motor to get the details of his engine and to see if he will lift the cylinders to see what type of pistons are fitted. His grandfather bought the bike new so chances are it will still be fitted with it's original barrels and pistons. I don't like my chances though.
Ern says he only ever saw one A motor here in NZ but as it was in the 1930's the bike was well used by then and he can't remember any distinguishing features.
I welcome forum members thoughts on this matter.

[23JDCA 808]

Tommo,
I am impressed with your research skills and dogged determination. ...bill

[Chris Haynes]

Tommo definitely knows his subject.

[HarleyCreation]

Keep it Simple

Tommo:

I think the "B" marked motors from the 1921 Service Bulletin is a different use of the same letter. Harley re-cycled letters over and over in different ways in different places for different applications willy nilly. That is where the too much Milwaukee beer joke comes into play. If I read you right, by 1921 that older use of "B" for high compression cylinders was obsolete. Quote: "This model is no longer being built." So in 1924 they slapped it on again in a totally different application for one year and probably used it again after that in some other way.

I have seen old official keys to explain Harley's lettering system back in the 1920s because it had gotten so complex and confusing but with little rhyme or reason. There needs to be a concise handbook about all this stuff using original Factory data. Unfortunately only 5 guys would buy it and they are all right here in this thread, except for Buzz who will request a free copy. ;-)

RE: "B" again:

In the 1924 model layout sheet there are 29 different models of Harley-Davidson motorcycles listed. Yep, 29 of them with 29 different model designations!

Please notice that in the "official" publication: "The Legend Begins" that on p.29 there are just twelve 1924 models listed and on p.200 only eight 1924 models listed. Once again we discover there is a much larger H-D history than anyone knows about, including modern H-D, Inc.

Anyway, just 4 of these 29 distinct models show the "B" suffix, for example:

Motor Number: "24FDCA 1000B"

These 4 models with the "B" suffix all state: "Iron Alloy Pistons." None of the other 25 models state that or state any piston material at all, except for one that is listed with "Dow Metal Pistons" (and you guys have to guess which model that is).

None of the other models have any letter suffix at all. None. Only the four "B" listed as "Iron Alloy Pistons."

In my judgement the "B" suffix in this context probably refers to the "Iron Alloy Pistons" feature also listed for those four models. Like I said before, the correlation is 100% and unique to this year. The letter "B" found on a cylinder flange or anywhere else will likely mean something entirely different. A different letter suffix (A, C, or XYZ, etc., will mean something else again in all likelihood (but with a possibly cunning exception now and then to keep us jumping).

I'm curious about the use of "Iron Alloy Pistons." Is that a different material from cast iron pistons? If so that's telling right there. How many different uses of iron as a piston material was there back then? What made "Iron ALLOY Pistons" special enough to describe then by name and then stamp the serial number with a "B" suffix to show that difference? What made that difference so important to them to note it in that manner?

Possibly I could be wrong and the 100% correlation is just there to throw us off the track, but it's enough to convince me that the use of the "B" suffix in this case means "Iron Alloy Pistons" but only in this case. Those other uses of "A" and "E" and "B" are entirely different applications. The 1924 use of "B" is in the serial number itself.

I found it very hard to believe that the factory would stamp the engine number twice with letters to describe the same thing, no matter how many beers someone had it just didn't make sense, so I spent some time ringing my HD contacts both here in NZ and in Australia to see if I could get some sort of answer.
An ex HD mechanic who started work at Jones Brothers, the NZ importers, at 14 years of age and is now well into his 90's told me that I should be ashamed for not knowing the answer and that I could find it in some of the HD "Service Dept. Bulletins" he had given me years ago.
As he likes to keep you guessing it took some gentle persuasion for him to finally reveal the following over the phone.
A = Police motor/ motorcycle
B = High compression cylinders fitted
E = Fast motor
I knew about the E motors but couldn't remember anything about the other two so went looking for the Service Bulletin and finally found it.
"No 90 dated Feb 25th 1921" and it describes all the above mentioned letters but states as per the B letter motors that quote "This model is no longer being built"
Back on the phone to Ern and all I got was bull**** those motors came to NZ right up until 1924 and if you want one to go real good now go looking for a pair of cylinders stamped on the flange with a B.
This led to me asking both Buzz and Bill if they could see if their cylinders were stamped with B thus at least going some way towards proving this theory.
Sadly neither are but another HD nut in Auckland does have a rear cylinder that is stamped B on the base flange and I have a front that has a 5 stamped there.
Both these cylinders are for the early stud pattern and are what we call "small base cylinders" here in NZ.
Before any of us can definately say this is the answer I would like Herb to carefully read the document he quoted to see if anything in it's wording can give credence to this theory. Meanwhile I'm trying desperatly to contact the owner of 24FDCA****B motor to get the details of his engine and to see if he will lift the cylinders to see what type of pistons are fitted. His grandfather bought the bike new so chances are it will still be fitted with it's original barrels and pistons. I don't like my chances though.
Ern says he only ever saw one A motor here in NZ but as it was in the 1930's the bike was well used by then and he can't remember any distinguishing features.
I welcome forum members thoughts on this matter.

[HarleyCreation]

The MoCo did have hourly beer rations in the workplace. John Nowak presented Bruce Palmer with his genuine H-D embossed tin beer ration cup.

That is super cool.

Another old guy told me that they would send the "kid" down to the brewery to get a "pail of beer" for quenching thirst on the job. Old man Davidson told me that during Prohibition his father (Wm. A.) would send him to the back fence with an empty pitcher and an arm would come thru with a full pitcher of beer in return. Somebody also told me that Gettleman named one of their labels after a small social gathering that included the four founders of H-D.

Get-get-Gettleman beer!