Board index Flathead Power-Technical Questions, Answers, and Suggestions Big Twin Flatties 1940 U Bottom Numbers: Military?

1940 U Bottom Numbers: Military?

Post Sat Jan 12, 2013 3:24 pm

Posts: 349
Location: Champaign-Urbana, IL

If Mr. Palmer is out there listening -- or anybody else for that matter -- there is currently a right side Big Twin flathead case for sale on Ebay. I checked with the seller and he told me the line-bore number on it was "40 **** A". So, I assume that it is a 1940 motor, but what about the "A" ending? Given that olive-drab paint is still visible on the half-case, does the "A" indicate "Army"? Do the "A" endings on line-bore numbers correlate in any way with UA military motors or is it something else?

Thanks in advance,


Post Sat Jan 12, 2013 7:43 pm

Posts: 391
My 40UA had normal line bore numbers, the only A was in the VIN.

Post Mon Jan 14, 2013 9:56 am

Posts: 349
Location: Champaign-Urbana, IL

Thanks ... I assumed that UA motors would come out of the same rack of line-bored case pairs, like any other model, so the addition of an -A to the line-bore number was something that I thought must have had meaning to somebody -- at least 70+ years ago.


Post Sat Jan 26, 2013 8:45 am

Posts: 32
Location: Western Australia
Mark, an A at the end of a BN has been mentioned on a few forums and some people including myself thought the letter may have been done by an inspector at H-D for one reason or another. That sounded reasonable because we see letters and/or numbers stamped in various areas on engine cases and trans cases.

Then it was mentioned on CAI in December 2011 and below is a link to that thread: ... ber-Suffix

In July 2012 on CAI the letter A was shown at the end of a 1941 45” BN. I remembered Bruce’s reply via the December discussion and because it had made sense I posted it.

Other BNs where I’ve seen an A include those for a 34VD, 1945 45”, 47 Knuckle, 49 Pan, 53 Pan and 61–62 Pans. At the end of the BNs of a 38UL I’ve seen a five-pointed star although I can’t say what that indicated.

But along with Bruce’s explanation I have to wonder if on occasion H-D just overstamped an incorrect character in the BN with the character that should have been used originally. For example, in my photo collection I have pictures of matching BNs 154-1++9 but the 9 in each BN appears to have been stamped over a 7. All the characters, including the ones I omitted, are the usual Harley types for a 54 Pan BN and there’s no sign that anything else unusual happened. I have a clear photo of the accompanying SN, all eight of its characters are the usual Harley styles for a 54 Pan, and there’s no indication that the number boss has been altered. Therefore in that particular instance I don’t think that the 9s were applied for any other reason than to correct a factory mistake.

Post Sat Jan 26, 2013 8:35 pm

Posts: 349
Location: Champaign-Urbana, IL
Thanks SBT!

I certainly hadn't thought of that, and coming from Bruce, it seems a very simple and logical explanation ... I can imagine that a guy stamping numbers would occasionally make a mistake, and they certainly weren't gonna trash a set of cases for something that simple. I am pretty sure that I saw a set of cases on Ebay in the last week or so that had what looked looked like overstamped final digits on the bottom numbers ...



Post Sun Jan 27, 2013 5:49 am

Posts: 67
What did they do about a mistake in the serial number?

Post Sun Jan 27, 2013 6:48 pm

Posts: 32
Location: Western Australia
Larry, one factory error we know of in a 1940s serial number was corrected by installing a new engine that was properly stamped. In Bruce Palmer’s 1932–52 military book he mentions 43WLC1046 but the first engine in that bike was stamped 43WLG1046 when a G stamp was used by mistake. When the error was discovered the engine was replaced by one with the correct SN. The two pictures below are courtesy of Chris Haynes’ collection of factory photos:



In the 1970s there were some Harleys that were originally stamped with the wrong VIN so the factory stamped a line through those VINs and then stamped a new VIN next to them.

Post Mon Jan 28, 2013 6:52 am

Posts: 67
Interesting. What was done with the improperly stamped engine? There must have been others during the history of the company; what was done with those engines?

Post Mon Jan 28, 2013 8:02 am

Posts: 3159
Location: Central Illinois, USA

As told to me by the ILL State Police;
Sometime around '73 (I can't remember..), a new employee grabbed completely wrong stamps at the Factory, and dozens (I can't remember...) were deflowered before it was noticed.

They probably went to the dealerships anyway, because I encountered one around 1988.


Post Mon Jan 28, 2013 11:50 am

Posts: 543
Location: Wa, USA
I worked with a guy in the late 70's who grew up in Milwaukee in the late 20's to early 30's. He told me that at that time HD had a large scrap pile behind the factory. He and his friends used to sneak in and take stuff from the pile. According to him, they built several running bikes from parts taken from that scrap pile.

That would be another way "scrapped" cases could get out on the street. If one bunch of kids did this, I am sure that there were others.

Post Wed Jan 30, 2013 3:48 am

Posts: 32
Location: Western Australia
Larry, I don't know what happened to the engine stamped as 43WLG. I haven't got a copy of Bruce's 32-52 military book but one of my mates has and I've read it but I don't recall reading anything about what happened to that engine after it was removed from the frame.

Post Wed Jan 30, 2013 6:54 am

Posts: 67
There must have been other errors in the 100+ years of the company. Did they disassemble completed engines and discard the cases simply because some guy hit the wrong stamp?

Post Wed Jan 30, 2013 11:36 am

Posts: 43
In the late 70s, our shop received 1 or 2, 78 or 79 models on which the engine number was struck thru with a horizontal line. A new number was added below it on the case.
On a few 79 models, the engine number was replaced by a 'confidential', or
line bore number, however, there was no vin style number on the cases.

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