Suzuki RMZ 450 2006. Cylinder head problems

Hello to everyone here! It`s my first topic here, so let me introduce myself first. My name is Oleg, I`m from Russia and motorcycle repair is my work from not to long ago, earlier it was my hobby. My ride is Honda VTX 1800 R, so I`m not experienced in MX bikes repair. And please, pardon my English!

Now it`s time for my question:

Couple days ago I`ve got 2006 Suzuki 450 for repair. Symptom is, like always when nobody maintenance motorcycle, - very hard to start the engine. Off cause disassembling shows that it`s time to change everything inside engine, but one thing is stumps me. It was impossible to adjust decrease valve clearance. Someone very smart was in this engine before. And he made some irreversible changes. Need to show You some pics to be understood better:

First thing that i met is very narrow valve clearance. I took off the cams and sow that valve spring retainer is (i don't know how it correct in English, but i'll try to portray) cut down with file to make it lower.

Than it was founded out that it was needed for only one reason. Valves are very high. And intact spring retainer had very high position, it was impossible to adjust valve clearances. To be honest they don`t have full success in this mod, cos valves still tight, and this pic made with no any shim under tuppet. It lays right on spring retainer and this is no any clearance above valve.

And same thing for all 4 valves.

what happens with valves? Why are they so high!? Valves and valve seats are in good condition what makes me think that somebody had to change em sometimes. I need Your advises - how does it can happen and what guides guy with file in his hand to cut retainer and do it curved?

I suspect that valves or cams are not from this motorcycle. So I need to check any dimensions:

cam height (in manual there is no actual height, only service limit) IN and EX

Also I need cam thickness. I forgot to make shot of it, but I hope You will understand me. Needed to know, is cams not to thick in place where we check valve clearance.

And I need valve height IN and EX

Thank You for any advises, opinions and answers!!!!!!