Another page aimed more at the restoration anoraks. Anyone who has looked closely at
Not only does the following apply to Z2’s but equally to Z1, H1, H2 and probably to any other
It should be pointed out that these date codes relate to the manufacture date of the part and not the Motorcycle, but in general it is normal to see a date of between 0 to 2 months before manufacture date of the bike.
Before reading further, it is necessary to understand a little about Japanese dating practices. Since 1868, when
Parts can be dated by either the Showa code or Gregorian code.
It is interesting to note that date codes are far more widespread on ‘later’ models. For example a 1972/73 Z1 will have far less than a 1975 Z1B
SWING ARM & TORQUE ARM
On the top of the swing arm, by the grease nipple, is the date code. The code uses the Gregorian format Y MM where the first number is the LAST digit of the year and the other numbers are the 2-digit month. For example: 4 11 is November 1974.
This swing arm is ‘5 05’ which would be May 1975.
On the back side of the Torque Arm is the number which follows the same procedure as the swing arm (although the month number is only 1 digit for Jan to Sept). For example: 3 6 would be June 1973. This torque arm is ‘5 5’ which like the Swing Arm would be May 1975.
SWITCH BLOCKS , REAR SHOCKS, STARTER SOLENOID
These are the final parts I know of on
These were ink stamped on completion with the full date of manufacture in Showa style. This NOS front hub for a Z900/ Z750 Four was made on 22nd September 1977, while the rear hub was made on 20th December 1974.
Several cast parts were ink stamped on manufacture. I have seen them on many engine internals even present after being submerged in oil for 30 years. I’ve seen them on clutch plate, oil pump, cam cover, points cover. I suspect many other items too.
Here are a three:
Interesting to see that the Points cover and Clutch plate (from the same bike) were both made on the same day, ie 21st April 1975, while the sprocket carrier (below), also from the same bike, was made about 3 or so weeks later,
WHEEL RIMS – TAKASAGO
Up until 1976, these parts use a Numeric/Alpha code based on Gregorian date. The number relates to year (with the first number dropped). For example 4 = 1974. The letter relates to the month running from ‘A’ for January, 'B' for Feb thro to 'L' for December. The first rim shown is ‘5D’ and is April 1975 fitted to a bike manufactured in May 1975. The second picture shows Takasago moving to a more conventional MM YY format. This rim is stamped 1077 and is therefore of October 1977 manufacture. It is the rim fitted to the hub shown above and clearly ties in with the date of the hub.
This is perhaps the most confusing of all date codes. It uses a Numeric/Alpha code based on Showa date. The number relates to year (with the first number dropped). For example 9 = 1974 (49 Showa). The letter relates to either a batch code, month code, or as I suspect, a 4 weekly code. (Unless anyone tells me differently) there are 13 letters I know of:
A, B. C, D, F, H, K, L, N, R, S, T, V
It would seem reasonable to assume that these letters would relate to a 4 week period with A being the first 4 weeks of January and V being the last 4 weeks of December and every other letter, 4 weeks inbetween. This is also backed up by the fact that the 'lower' the letter, the earlier in the year the manufacure date is.
If you know differently, let me know.
Anyway, this disc is, I suspect, Dec 1975