Difference speedometer Z1 900 vs Z2 750

Is there any physical difference between the speedometer for the Z1 900 and Z2 750 other than the graduation in km with red markings and the red light on the Z2 …

They are identical to each other.

Are you trying to put a Z2 on a Z1 or the other way around? While identical physically they have differences internally, the "speed sensor" for the Z2. But the ratio of drive remained the same.

The following images are courtesy of the pre-press proof edition of John Brookes upcoming new edition Restorer's Handbook.  Apologies for the blurring.  The book is quite thick & doesn't fit the constraints of the scanner very well.

These are best-documented examples to date.  If anyone has dated hard-copy examples that differ, please share & we'll forward to John for his evaluation & possible inclusion in the new edition.

There's some discussion in Japan of which speedos made it into production.  We'll let the caption of the photo below speak for itself.
 

The Japanese sales handout appears to be the same type prototype speedo seen above.  See top center next to the bike.  Lighting isn't good, but the red increments are clearly there.
 

The documented production speedos have a 'red line' instead of the red characters & increments of the prototypes.
 

Good Ridin'
slmjim & Z1BEBE

 

Thanks for the answer!

The idea was to see which gauges can be overhauled and used on Z2. As it looks, the Z1 gauge can be used but without the red warning light for speed. Speedometer from Z650 / KZ650 with speed markings to 220 km/h can also be used.

Yes, a KZ750 Twin or KZ650 using the 140mph or 220KPH face. If using the 240KPH a KZ900, KZ1000 or Z1 160MPH would be fitting. Just have to match correct drive unit to it's face. You might have a close look at the center "black" cover on your needle. The Z1 had a slight "dished" style. they used a flat one starting in around 1975. Also noteworthy is the early KZ650 gauges had a convex glass lens unlike any other gauge i've encountered. Easy to tell from afar because these 650 ones retained the black outer background like the Z's, changed to that greenish background later.