X-WLCH wrote:it's possible that one out of every 200 will be a match. ( the one motor builder got 200 numbers at a time theory )
knucklebolt wrote:As long as the serial number is good/authentic I don't worry too much about belly numbers. My '37 has absolutly good serial numbers, but the the belly #'s are matching 1941 numbers. Those old engines have been through a lot of use and abuse and it makes sense that there are more miss matched numbers out there than matching.
Did that make sense?
Speeding Big Twin wrote:X-WLCH, thanks for the reply. I‘ve heard before about the relationship between SNs and BNs and I began recording examples of many years and models a while back. I checked my photo collection for 1937–48 U-series SNs that I also have BNs for and I found 93 examples which appear to be factory-stamped, excluding the example at the start of this thread. The only model year not represented is 1943.
Examples within 200 of each other: 55.
Examples more than 200 apart from each other: 33. (Of the 33, seven are close enough, being no more than 221 apart from each other.)
Because in some instances some characters were hidden by the owners, five examples could go either way and it’s possible as many as three of that five could result in matching numbers although of course it isn’t very likely that any would.
It’s also interesting to note that on 50 occasions the SN was higher than the BN and 39 times it was lower. In four instances it could go either way, again due to some characters being hidden by the owners.
X-WLCH wrote:Hi Don
Do you know how Mr. Andres marked the line bore numbers on replacement cases, and was there a HD policy ?
Can it be assumed that the replacement case got the same serial number as the original ?
knucklebolt wrote:Yes Eric I did miss the point a bit. I was just saying that I wouldn't be worried about SN's matching the BN's as long as the SN looked clean and authentic, but no that wasn't the point. !!
I have had some experience with stolen bikes/altered SN's, and I was just saying that I'm convinced the SN's on my big twin 74 are real, really an almost "textbook" example of good numbers and a unmolested SN boss, but I wouldn't have any idea if they were stamped on replacement cases at the factory, stamped at a dealer, or just how the cases were replaced and stamped. So no, I don't know, and yes I did miss the point. !!
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