Bridgestone Frame and
Engine Serial Numbers

by Graham Weeks

Originally appeared in the UK Vintage Japanese Motorcycle Club Newsletter vol. 19, no. 4 (Aug 1996).

There are three different identifaction marks on all Bridgestone motorcycles. There are the usual engine and frame numbers, with an additional Vehicle Serial Number on a separate plate riveted to the frame.

The Vehicle Serial Number follows the same format for all models, and uniquely identifies an individual machine as it leaves the factory. A typical serial number (actually from my own 350 GTR) is shown below:

21 D 05121

The Model Code (first two digits) identifies the basic model from which the machine is derived, and the code numbers used were as follows:

12 ... BS 90 DeLuxe, Trail and Mountaineer
13 ... BS 50 Sport
14 ... BS 90 Sport
15 ... BS 60 Sport
16 ... BS 175 Dual Twin and Hurricane
17 ... BS 90 DeLuxe, Trail and Mountaineer (Oil Injection versions)
18 ... BS 90 Sport (Oil Injection)
19 ... unknown
20 ... BS 100 Sport
21 ... BS 350 GTR and GTO
22 ... BS 100 GP and TMX
23 ... BS 200 Mach 2 "RS" and "SS"

The Month Code (third alpha character) identifies the month of manufacture and repeats in a 2-year cycle, starting on an even year (1964, 1966, 1968, etc.). Thus, the codes refer to the months in the table below:

Month Even

The Identification Number (last five digits) identifies the individual motorcycle and simply increments for each successive machine built, starting from 00001.

The precise month of manufacture is obtained by combining the month code and the Identification number. No official information is available on production records for each model, but the factory Parts Lists do give specific dates and serial numbers when modifications were introduced on the production line. It is quite easy to work back from these "milestone" dates to date any individual machine reasonably accurately. Relevant "milestone" dates and serial numbers available for the models sold in the U.K. are as follows:

BS90 DeLuxe12 N 036928Feb 1965
12 B 057034Feb 1966
12 R 065628Jun 1967
BS90 Sport14 S 002364Jul 1965
14 C 007418Mar 1966
14 G 011238Jul 1966
BS90 DeLuxe
17 F 009030Jun 1966
17 B 021551Feb 1968
BS17516 A 03736Jan 1966
16 M 22448Jan 1967
16 O 27401Mar 1967
16 R 31816Jun 1967
BS35021 S 01022Jul 1967
21 E 05455May 1968
21 W 07415Nov 1969

Frame and Engine Numbers

The frame and engine numbers follow different systems for each Bridgestone model.

For the single cylinder models, the enigne number is stamped on the transmission case, and is of the same format as the Vehicle Serial Number previously described. The frame number is stamped either on the headstock (50cc and 60cc models) or on the right hand side of the frame behind the swinging arm pivot (90cc and 100cc models). This number is of the form "KE 064287". The prefix letters seem to refer to the Basic Model for which the frame was built, but I have insufficient information to confirm this. The final 6 digits of the frame number form an individual frame Identification Number, again simply incremented for each frame produced.

Website visitor comment about the 175 & 200 frames:

The article is misleading. 35,400 TA1 frames were built, with the first 4,500 BS200s using those frames. The TA2 frames began in 1970, and 3,300 were produced to finish BS200 production. 7,800 total BS200s were built.
The frames had sequential numbers through the 175–200 build, with 30,830 175s and 7,800 200s. For BS200s, add 30,850 to the serial or engine number. If both numbers are within 100 of frame number, it meets original specs!
—Perry Anderson, 11 Feb 2023

For the 175/200cc models, the frame number is stamped on the side of the headstock, and the engine number on the transmission case. Both of them are of the form "TA1-30991". Here, the last five numbers form the incremental identification number, and the prefix is the factory production code. The "TA1" prefix was used for 175cc machines, and "TA2" was uded for 200cc machines. Note, however, that the very early BS200's were built using up the last of the stock of 175cc frames (175 and 200 frames are identical), and these therefore would have had frame number prefixes of "TA1".

For the 350cc models, the frame number is once again stamped on the side of the headstock, but the engine number this time is on the upper crankcase, just forward of the rear engine mounting lug. This number is usually stamped quite lightly, and can be difficult to see under the usual layer of oil and road dirt. The format is similar to the 175/200cc but using the 350's own prefix code of "NA-1".

It may be of interest to note that the factory production codes can be cast into many components, from speedo drive gears to engine casings. "NA1" will indicate a 350 part, "TA1" as 175 part, "EA1" or "EA3" a 90 part, "GB1" a 50 Sport part, and so on.

A final note: As the machines left the factory, the Identification Numbers with the Vehicle Serial, Frame and Engine numbers were unlikely to be the same on an indivudal bike, but were always within 200 or 300 of each other. Any machine with numbers further apart than this has probably had an engine or frame change during its lifetime (apart from the early 200cc machines mentioned previously built with the late 175 frame numbers).

Submitted by Graham Weeks through the Bridgestone Registry. You can write to Graham at 104 Wrington Close, Little Stoke, Bristol, BS12 6ET, England. [Mr. Weeks died circa 2016.]

Bridgestone Motorcycles pages by Mike J. Brown