cg125 1997 cracked inlet valve

[normwist]

Hello fellow bikers...
I use a cg125 1997 for commuting, started to notice it missing a beat at more than half revs in any gear including neutral so tried replacing/checking basic things like new lead n plug, new coil, clean carb, airbox clean but none worked. The valves only needed a slight adjustment but a week later i checked them again and the inlet valve was closed like there was no room on the rocker. Ive just taken the top end off and have noticed that I have a cracked and bent inlet valve. Damn.. The bike has always had oil in it, there was oil in the topend and this problem started after I initially checked the valves so do you think i set them on the de-compression stroke which caused this?

Here's a few pics:
https://ckcbpa.blu.livefilestore.com/y1p-yqqxY61lW_xJE2QW3SqcKRVuz3f5PSkaYnUUQ2XmRPQAiY99hvHNPoqpZhcOXi-21kzyl0wHzUGW2KcHez6g4xPA322B_j1/IMG_0016.jpg

Valve seat marking ontop of piston and on head above the line of where a unbent valve would sit/seal.
https://ckcbpa.blu.livefilestore.com/y1pgSt9GwXvqp-If02mGkApYVfSk65_50AaluDw2tu91w8BCEz1WIljAOhcwUH9_SF7t6khKGRm2Vp8CSFA0fmJkb0nAeNgMMlZ/IMG_0008.jpg

https://ckcbpa.blu.livefilestore.com/y1p9fNJw8bFKAQ3dXgUzqYZinJ3JLrJEihe7BBcQhntjQa6uEyG44wBB75-ldw_VxAUMSIbORX61DIHyA-l0ATrFoCaZz3Axz14/IMG_0010.jpg

Here is a pic of my cam followers:
https://ckcbpa.blu.livefilestore.com/y1pETbEHXrXCbgcA8kQhrhuNsz8HIDYii_keSGPuKVXLkcZ_Vep0Xlyo-Ux-6ldrTgqrqBG2uC47fc8IJASqC4dxBXT-pdTIBjs/IMG_0023.jpg

Can anyone tell me if it is standard practice to be ok to just stick a new inlet valve in without the need to grind it into the seat? (Dont have tools for this!) Why this happened i dont know other than as i mentioned maybe i set the valves on de-compression stroke or just wrong (tho ive done it ok in the past!). The cam followers are not marked, the cam lobe is smooth and the gear it sits on and the crankshaft gear is not worn. I turn the crank over and it is smooth, when the engine ran there was no knocking otherthan noise from the topend like it was coming from tappets hence the checks on them. The valve guide looks ok. Is there are other reason why this inlet valve broke? Im proper stumped over this one...... any ideas, anyone, please....