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In 1969 the BSA and Triumph factories moved to a common numbering
system used for both engines and frames. This system was used throughout the production
run of the Tridents and the Rocket 3s.
Engine and Frame numbers are composed of a model identifier,
a two character date code (month and year) and a five digit, sequential serial
number. On some models the model identifier appears at the beginning and on other
models the model identifier appears at the end. The date code always appears immediately
preceding the five digit, sequential serial number. Frame and Engine numbers would have matched when
the bike left the factory.
| The two formats: |
<model> <date><serial no> |
<date><serial no> <model> |
| Examples: |
T160 KK06100 |
DG02010 T150V |
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The Date Code
The first code letter indicates the month of manufacture.
The second code letter indicates the model year of the bike.
The model year started in August of the preceding year - or whenever the factory came back to
work after the summer break - and ran through July.
For example:
ACxxxxx indicates January and a 1969 model year bike. It
would have been shipped in January of 1969.
KHxxxxx indicates September and a
1973 model year bike - this bike would have been shipped in September of 1972.
|
| Letter |
Month |
Model Year |
| A |
January |
1979 |
| B |
February |
1980 |
| C |
March |
1969 |
| D |
April |
1970 |
| E |
May |
1971 |
| G |
June |
1972 |
| H |
July |
1973 |
| J |
August |
1974 |
| K |
September |
1975 |
| N |
October |
1976 |
| P |
November |
1977 |
| X |
December |
1978 |
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The process appears to have gone something like this: As an engine
was completed on the engine production line it was stamped with the five digit sequential
serial number. The engines were then stored - awaiting buildup into a frame. As the frame
was completed as a completed rolling chassis an engine was pulled from storage and
installed in the frame. As a result the engines were not always used in exact numerical
sequence. When the engine was added to the frame the month and model year code was added - as was the
model identifier.
This would explain why sometimes bikes with early serial numbers were shipped a couple of
days later than bikes with subsequent serial numbers.
The last BSA Triples . . .
The last batch of BSA Triples shipped to the US market went out in two
shipments in early November 1971. The bulk of these bikes were shipped on 1st November.
Another three bikes were sent the following day. These were the last of the BSA Triples destined
for the USA.
After that, about another 200 bikes were built and shipped to various other markets before BSA closed
it's doors forever. The last shipment of four bikes was on 8th September 1972.
The last Triumph Triples . . .
The last Triumph Tridents were T160s. Production for this model was started, as usual, in August
of the preceding year (1974) and ran through July 1975. However, some of the very last bikes were built
in late 1975 and into early 1976. These bikes will have 'N' as the model year - even though there was
no official 1976 model year for the T160. All told, about 7,500 T160s were built.
A word of warning...
Be careful about relying on a specific serial number to validate
your bike's age. The original records are the best place to go if you have doubts.
Although even these records contain human error. Often, if the official 'engine stamper'
stamped the same serial number two times in a row, they simply used different months to
make those bike's numbers different. There is one instance of two 1972 Rocket 3s that were
stamped with the same serial number and the same month/year combination - identical
engine numbers! To make matters worse, both of these bikes were originally shipped to
dealers in the same country - the UK.
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Here's an engine where the serial number was
supposed to be "014xx". Our reliable 'worker' apparently got
distracted and stamped the "4" twice in a row - ending up with
"044xx". They then tried
to correct the mistake by stamping a "1" over the first
"4" - it doesn't show too well in the photo as it merges with the
downstroke of the "4".
The only reason this was noticed was
because "044xx" is too high a number for the date code of
"AC" and, of course, it doesn't appear in the factory records.
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A "1" overstamped on a "4". The outline of the
"1" has been highlighted in red.
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The earliest run of BSA Triples were assembled in varying months -
but were collectively stamped with a given month ID. Why? Who knows?
Interestingly, again in the case of BSA Rocket 3s, some very late
1971 engines were used for the first 1972 models. The production run of 1971 bikes ended
with A75R JE01184. However, some engines that had already been stamped prior to 01184 were
not used for 1971 bikes but instead were used for the very first 1972 model bikes. So
these very first 1972 bikes have oddly high serial numbers (such as 01172) - higher than
the production run of 'normal' 1972 bikes which ran from 00101 to 00634.
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