Z1 engine and frame numbers

Z1 engine and frame numbers
All Z1 & KZ900 frame numbers are stamped on the steering head.  Additionally, in the USA & Canadian market, there is a white sticker on the steering head showing the frame number and the date of manufacture.  The frame numbers will be in the following ranges

1973 Z1	Z1F-00001 through Z1F-19999
1974 Z1-A	Z1F-20000 through Z1F-47499
1975 Z1-B	Z1F-47500 through Z1F-85700
1976 KZ900-A4	Z1F-85701 through Z1F-13xxxx for bikes  manufactured in Japan
1976 KZ900-A4 & 1977 KZ900-A5	Z1F-500001 through Z1F-51xxxx for bikes  assembled in Lincoln Nebraska

Z1 & KZ900 engines have engine numbers stamped on the top right side crankcases on a raised area over the clutch.  The engine numbers follow the same general range as the frame numbers.  Frame and engine numbers were not matched at the factory, although most frame / engine number combinations are within 200 numbers.  Most bikes have the engine number higher than the frame number, but this is not always true.  We have records showing new bikes sold where the engine number is less than the frame number - although this is fairly rare.

While the frame and engine numbers are the best indication of the model and whether the engine has been replaced, these are not the only numbers to help validate an 'authentic' Z1.