"the intake is 0,10mm - 0.19mm, exhaust is 0.15 mm - 0.24 mm"
Copied that from the sticky.
(NEW) KLX250s FAQ and links KLX250s FAQ and links - Kawasaki Forums
There is a pdf manual available too.
So you're on the tight side, but in spec. If it were me I'd try and get it in the middle to open end of spec. My bike was a little tight on the exhaust and I changed the shims to put it in the middle, it has since started much better, hold and cold.

 

Thanks, since I still have the cover off I think I will open the clearance into the middle of the range... or more?
Does it always drift off to tight again or is it likely the clearance may widen out with normal engine wear?

 

It'll get tighter over time.

 

I just bought a Weisco shim kit. I read too many reviews on Amazon about other kits' shims varying in size compared to 'as marked' and being softer then Kaw shims.

Also found a BMW car forum where someone was advocating using motorcycle shims instead of the normal very expensive shims for Beemers. He later posted some hardness data for various shims and the Weisco were right on spec.