real quick question!

ok did some searching but found nothing to answer me exactly! i have a 78 and a 79 650 SR one has the breathers on top of the valve cover the other doesnt, i really dont like the looks of the one with the breather and i am going to clean ONE of them up, will the one without the breather fit on both engines?

i THINK this is as simple as yes or no...it seems like it would fit but i want to be sure!

Many riders here take the "Smog Gear" off and get block off plates, capping the vacuum lines.
Some get a piece of hose & hose clamps and connect the two ports together.

Smog Block Off Plates
www.tpoparts.com
www.kzzone.com/billet.html (They were wowrking on making block off plates for the smaller 4's, so ask about your's).

Looks like you can swap the covers, but to use the early cover on the later motor you need to block off the four smog ports in the head.

Pay close attention to the differences in the two gaskets linked here:
1978:http://www.z1enterprises.com/Valve-Cover-Gasket--KZ650-7778-460.aspx
1979:http://www.z1enterprises.com/Valve-Cover-Gasket--KZ650-7980-458.aspx

ok thanks a ton guys! very helpful, i will see what i can do. maybe just use the 79 head when i re-work my engine

I used epoxy to block the holes leading to the exhaust and then used a non emission cover on a 82 750 twin motor. It's been working fine for three years now.