Pod air filters?

Thanks for the advice guys. Anyone know how to take the gas tank off of a 78 kz650 D?

Open the seat, disconnect the fuel line at the petcock (hopefully you don't have a leaker) lift at the back of the tank until it pops free at the back, then slide it backward carefully. Might have to wiggle it a little to get the tank to slide free from the pucks. Also, watch to make sure the pucks don't fall off, if they do watch where they roll to.

Cool cool, how does one "rejet" a carb? Do you have to take the whole carbs apart and replace the turbine jets in them?

The physical act of jetting is super easy, it's getting the right size jets for your set up that can be a bit tricky. In the VM series carbs (which I believe is what you're running) the pilot and main jets are inside the float bowls. Pull the carbs and remove the 4 screws holding each float bowl on. You'll see a large slot headed screw with a hole in it right in the center of the carb, sitting on a brass tube with 8mm hex head on the ferrule. This is the main jet. Take a 8mm wrench and hold the emulsion tube and use a large headed slot screw driver to remove the jet. Replace with desired jet size. Repeat for other 3 carbs.

Pilot jets are down inside a hole on vm24 carbs or have a long body on them on larger vm carbs. These sit to the side and slightly off center from the main jet. For 24s you'll need a small slot head screwdriver to remove them from inside the hole. Again, replace with larger (17.5) pilot jets.

And THEN you've got the needle adjustment part of it that requires a bit more disassembly...Check out this list of resources from over on kz650.info, lots of procedures outlined step by step...
maintenance.kz650.info/GeneralMaintGuides.php

I've had K&N's and Uni pods. Hated all of them. The K&N's deteriorated quickly and were a huge waste of time to clean and oil. The Uni's were easier to clean and oil, but they crumbled after a few years.

I've been using the cheap, disposable, Emgo's and haven't been happier. For the price of the filters, and oil, and cleaner, and labor, the Emgos are a way better deal. If one starts to look bad, toss it, throw on another one. Mine all still look good after 3years.

K&N's only flow more if you don't oil them, but then all sorts of crap is getting into the motor.

With all pods, you have to avoid water.

If you can deal with the airbox, it is the best setup for a daily driver. It has a little better torque from a stop so it's a little more friendly for daily stop and go driving. And it doesn't care about rain.

But the pods do scream better on the top end. Noticeably. You have to jet more on the rich side with pods to get them right. The mixture changes a lot based on how you sit on the bike and crosswinds etc. (I confirmed this on an o2 sensor air/fuel gauge.) If you jet it a little rich, you'll probably never notice hesitation under these conditions, but if you jet it for fuel economy for cruising, certain seating positions or crosswinds may cause a slight hesitation.