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What’s your year, make model? If you have ever called in to place an order with The Bonneville Shop, or for some technical advice, chances are you have talked with me. Once the conversation is underway, my typical first question is: What is the year make model of the motorcycle you are working on? The answer is usually pretty straightforward, but sometimes the caller doesn’t really know the full answer to the question. I might get an answer like “It’s a 60’s Triumph Trophy”, or “I inherited this chopper from my uncle, the title says it’s a 1965 Daytona”, or even “I don’t know, but all I need is a front brake cable, aren’t they all the same?”
When met with this ambiguity, I’ll generally ask for an engine and/or frame number, to which the answer is often “Where is the engine number?” or “Where is the frame number?” The purpose of this article is not to denigrate callers, but rather to help new owners to understand what year make model they have and what they need to buy in order to get the right part the first time around.
While this article is largely aimed at vintage Triumph identification (Year Make Model), many of the production codes apply to vintage BSA models as well. I’m not as familiar with the Norton identification system, so I will leave that for another day. Due to the commonality of the early and mid-1950s pre-unit Triumph 500 and 650 models, a simple numerical identification was used on the frames and engines.
Triumph and BSA Frame and Engine Numbers
In almost all cases, the Triumph frame and engine numbers matched, however this was not the case with the A7 and A10 BSA twins. Like the pre-unit Triumph twins, there was commonality between the 500cc A7 and the 650cc A10 pre-unit BSA models, so all the frames were stamped with a letter, then ‘A7’, eg. ZA7 26001. This followed until the introduction of the unit-construction twins, when the frames all carried the prefix of A50, even with A65 engines fitted. Finally, the BSA twin engine and frame numbers matched for the 1967 model year, make year make model id easy.
With the advent of the unit-construction ‘C’-range 350 and 500 models in the late 1950s, the prefix of the VIN began with H, starting with H101 in 1957. The ‘B’-range 650 models continued with digits until the introduction of the Duplex frame in 1960 when the new prefix of ‘D’ was implemented, followed by the sequential digits through the 1962 model year. When the first unit-construction 650 models were introduced for the 1963 model year, a new prefix of DU was used, starting with DU101, and continuing on until DU90282.
The 350 and 500 models continued on with the H prefix through H67330 into the 1969 model year. Early in the 1969 model year, a change was made to an alphanumeric system which incorporated two letters, then a sequence of digits to create a more detailed production date, as there were running changes in parts specifications due to product upgrades and an ongoing conversion to the use of Unified threads on the cycle parts.
The C-range models commenced with XC06297, and the B-range models started at NC00100. BSA also adopted the new numbering system, where the first letter was the month, followed by the second letter, denoting the model year. This system was used until the end of production for both of the marques.
Where are the Frame and Engine Numbers?
Now comes the answer to the question of “Where are the frame and engine numbers?” Both Triumph and BSA engine numbers were stamped on the left, or “drive-side” of the crank case, above the primary chain case and below the cylinder barrel. The later production 1969 models commenced a raised pad in the casting for the engine numbers against a background of BSA or Triumph logos, which made it much harder for alterations to the production codes to be made.
The BSA frames had a lug on the lower drive-side downtube where the frame numbers were stamped until the introduction of the 1971 oil in frame models, when they were moved to the general vicinity of the headstock. Triumph frame numbers were stamped on the unit frames on a raised pad, usually on the drive-side down tube, just below the headstock, but on the oil in frame models, they could have been on the front of the head tube, or even on the top tube above the left gusset that joins the down tube, head tube, and top tube.
Engine Frame stamp to ID Year Make Model
Registration and Title Documents for Year Make Model
One last confusing element in identifying your year make model is the information on the title. Ownership documents, like titles, were often issued the year the motorcycles were first registered, not the year of manufacture. Let’s say a 1968 Triumph T100C was purchased in February 1969. In many states this would appear as a 1969 Triumph T100C on the title. This could be problematic when it comes time to purchase hardware, as the shift from British Standard Cycle thread forms was underway starting in 1967 and gradually transitioning to Unified (American) threads all the way into the mid-1970s, when nearly all of the threads on fasteners were either UNC or UNF.
If there are any questions about the year make model of your vintage BSA or Triumph motorcycle, we welcome you to use our text line or email to send some pictures of the numbers on your frame and engine. The text line is 720-260-4271, and email inquiries can be sent to orders@thebonnevilleshop.com. I hope you find this article helpful and thank-you for reading it.