Carb swap on 81 KZ650

Found a steal on a set of 1978 carbs with no accelerator pumps. Wanting to switch over to my 1981 KZ650 CSR that currently has accel pumps. Wondering if anyone has done this swap, and if so did you have to do any rejetting? I understand its possible to disable the accelerator pump on my carbs, but the rebuild kits are available for this set of carbs.

Yes. the 78 carburetors should fit fine. you can use any VM24 carburetors. and the jetting should be fine.
But you may not really need rebuild kits. I have the same bike and just cleaned the carbs and replaced the gaskets, o-rings & whatever rubber parts were available. My carburetors were in very good condition. Z1Enterprises.com had the gaskets & starter plunger caps. I got the starter plunger o-rings from the dealer. Z1Ent might have those & a K&L accelerator pump kit.
A HarborFreight metric nitrile o-ring kit had several sizes that fit fine. pump nozzle, main-jet/bleeder-pipe, & drain screw o-rings.

Rebuild kits can be a waste of money & sometimes the brass parts aren't correct. wrong jet sizes. wrong needle taper. that sort of thing.

Great, the info is much appreciated. I'm assuming the 81's airbox was a direct fit as well?

Any VM24 carburetors should fit the 81 airbox. Something worth noting: the 81 KZ650 airbox ducts are unique to the 650-CSR, so if your ducts need replacing, you would have to adapt the 82-83 airbox ducts, using radiator hose to make donuts to make up the difference. The 82-83 650-CSR have BS32 carburetors, which have a larger OD where the ducts fit.

Good to know. I plan to eventually get an older year airbox in which the ducts are still manufactured. My air ducts for the 81 are still pliable, but not perfect. On an older thread I had outlined a setup using the radiator hose, although I reverted back to the 81 ducts due to my annoyance and impatience in dealing with the donuts (my own personal issue, not the donuts').

Cheers!

I remember someone having trouble adapting the BS32 ducts. You have to find properly sized radiator hose & make 2 donuts per carb. a helpful auto parts guy would be handy. Then you have to use good clamps. You may already know this, but the 81-83 650 airbox is actually a 750-4 airbox. mine is embossed with KZ750E/H or something like that.