Fork oil change

Hey guys, so I've got my bike working and everything like it should be so now I'm trying to update the suspension. I've got a 78 kz650 and I'm trying to change the fork oil and inspect my Springs but I'm stumped on how to open up the forks themselves. Rather than having a bolt on top that you twist off to open up the forks, it has this piece that is like an inverted square that goes down into the top rather than sticking out and I have no idea how to get it off. Is there a special tool I need or am I just an idiot and am missing something completely?

push down on it and then pop out the circlip

In the diagrams it's listed as a Seat spring & appears to be threaded.
Stick a tool in the square hole, then unscrew the plug. You may need a special tool.

Next, you're going to have some more fun removing the bottom allen bolts.

I don't believe there's a circlip on the KZ650-B2. Instead, that top bolt with the square hole should unscrew. See if either a 1/2" or 3/8" ratchet extension will fit the hole properly. Be sure to loosen the top triple tree clamp bolt before trying to unscrew it. Ed

At first glance it seemed like the square hole might be bigger than a typical ratchet,
but I think 650ed is right & a 1/2 will probably fit.

1/2" breaker bar is the easiest way to break it loose,after loosening top triple tree bolts

Yea, it's simply a screw on cap with a 1/2" drive built into it. Normally it is tight to break loose, but just keep your lower clamps tightened, then insert a 1/2" extension, use the biggest ratchet or breaker bar or use a pipe to extend to gain more leverage.