To start with the basics here is the VIN number and production quantity data I was able to compile...
79 A1 Frame = KZT30A-000101 Engine = E00101, 6100 fames numbers, 5700 engines so we assume no more than 5700 motorcycles produced
80 A2 Frame = KZT30A-006201 Engine = E05801, no more than 5300 frames produced but 6600 engines
80 B2 Frame = KZT30B-000101 Engine= ??? if we assume the extra engines were all used for B2's then the can be no more than 1300 B2's
81 A3 US made Frame= JKAKZAA15BA-011501 Same stating number as Japanese sequence???
81 A3 Japanese made Frame = KZT30A-011501 Engine= E12401 total US and Jap. production, no more than 2400 produced
82 A4 Frame = KZT30A-014101 Engine = E14801 More frames than engines, but no more than 1600 produced (US production ???)
83 A5 Frame = KZT30A-015901 Engine = E16401 Serial changed in 84, total production unknown (we could assume similar 1982, 1600)
84-85 ZG Frame = ZGT30A-000001 no more than 2800 made
86-89 ZG Frame = ZGtT30A-002801 No Idea how many were made, probably very few.
So the total for all years is something in the neighborhood of 25,000, this number is quoted form several sources.
Here is my '81 shortly after I first got it.
Differences I know of are as follows.
The 1981 Kz1300 was a short production run because of changes to the ignition in 82. I have no hard evidence but I have seen several sources claim that about 800 were made that year. Mine is Manufactured in Japan, but some may be US made.
Available in Red or Ebony, engine covers were chromed, so were the air box side covers.
Rear shocks were air ride, and the front forks were linked with a hose to equalize air pressure.
The ignition pickups and timing advancer were done away with in 81, three hall effect sensors read a pickup wheel under the left side engine cover. Ignition has an electronic advance. The pick ups were moved to right had side of the engine for 82 to end of production.
1980 saw the start of the deep sump oil pans, and increased oil volume from 4.5 to 5.6 liters and for 1981 it was increased again to 6.2. The oil sight glass is also larger for 1981 and onwards.
That's all I know.
The windscreen is after market, but the Vetter hard bags were probably a dealer add on.
here is how she looks now