KZ1000 head - what's happening here?

So as I've gotten deeper in to the stuff I bought, I dug out a head that was clearly not a 900 or early 1000. Figured out it's a later KZ1000 head, but there's been some work done to it.

Neither the intake nor exhaust port look very smooth, but the top of the combustion chamber looks like it's had some work done to it. Any ideas what the purpose of these mods are? I would have thought that taking material out would decrease compresion. To drop in different (taller) pistons?

Rob K

looks to be a stock gpz bath tub emission head :pinch: ......I don't see any mods :pinch: .......... :dry:

fourth pic shows a stock combustion chamber for that head.......... :huh:

It's a GPZ1100 bathtub (twin swirl head) also used on the later z1100's.
Lower compression than the early 900/1000 but slightly higer than the 'J'.
It is THE head to have for performance upgrades.

Thanks all - was looking in the wrong place. Assumed it was KZ1000.

Would guess that you could use a 900 lower end with this gut, plus cylinders and valve cover from the GPZ?