kawi head skim measurement

I've noticed head skim markers under the exhaust ports on my gpz550
cylinder heads, on std heads they are ?? 1mm below the gasket face, on
a heavily skimmed head they are flush. Anyone?

 

Some engines have minimum head thickness specs. If that Kawasaki model
has a recommended minimum I'd check on a few potential complications
before exceeding it.
On chain-driven OHC engines "Excessive" head milling/skimming changes
the cam timing and adds slack in the cam chain for the tensioner to
try to remove. It also weakens the head some and can tend to provoke
head gasket sealing problems. It brings the valves closer to the
pistons. On water cooled engines there are water jackets in there
somewhere. Not all these problems will arise with a 1 mm cut, but

 

There is no head thickness or skim recommendations in any of the
service manuals. Cams will be dialed in and checked for clearance and
an uprated tensioner used.

The manual lists around 16cc combustion chamer, this head has I think
..7mm skim but the chambers are still over 15cc ...ie much less
combustion chamber reduction than simple calculations predict.