kz650 trans swap to 6 speed

The bike is $200. I guess I could give it a shot lol. I'm sure I could scrape something out of it if it didn't work out.

The zx600 and the zr550 have a 10mm longer output shaft. This was needed as the swingarms and rear wheels got wider and I suppose it was easier for Kawasaki to extend the output shaft than to produce a whole line of offset sprockets. Otherwise I believe them to be the very same as the kz550 transmissions...gear ratio wise and so forth.... but I have never compared them side by side on a bench, so I am not 100% sure.
When factoring in the gear ratios of putting a 6-speed transmission into a kz650 or 750, don't forget to factor in that the 650/750's have a different primary gear ratio that is tied to the gears on the 650/750 clutch basket and secondary shaft. This will drastically change your final numbers if you are on gearingcommander.com and are running the numbers. (Also don't forget the huge difference between 530 and 630 chain pitch and front and rear sprocket ratios, rear wheel and rim size has on final speed and rpm numbers.)

kz/gpz550 output shaft




zr550 output shaft

The Zr does have some minor differences (other than the output length), so they may swap, but they are not identical. I made this image to compare the Zr with the Kz. Notice that there is an extra splined bushing with one of the gears on the Zr, where the kz just has a splined washer. Maybe that is just a requirement due to the longer output shaft?

My mistake Lou, the Zephyr is a 6 speed.