29mm

how much can you gain from putting these carbs on?1975 z1900

Since your wallet will be significantly lighter, your overall weight will be a lot less so you should go faster. On the 75 Z1B, the carbs will not be delivering all the gas that the engine could potentially use at 7500 rpm. You will feel a difference between 7500 rpm and redline. I suspect you would gain perhaps 5 hp on the top of the rpm range and you will feel the difference. For ordinary every day riding where you are not at wide open throttle, not much difference; in fact, perhaps some mid-range is lost over some 26s or even little 24s.

thank you how about coils and electronic ignition? i just drive the bike around town and to work doesnt sound like carbs will work .what other little things could i do to run alittle better

wiredgeorges coil mod, Dyna S to get rid of points and green Dyna coils & wires. Did wonders for mine

Here are a couple of graphs, one for the KZ900 and another for the KZ1000, comparing the VM26 carbs vs. the VM29 carbs.

KZ900

KZ1000

bike has 28mm on them how do they compare to the 29mm smoothbore?