Trying to fix my bike
 

Hi guys, I do not know too much about engines and bikes, thats why I really like this site. I had my gz 250 for three years and it was my every day ride, but it just stop working the last week. So I tried to fix it with patience, free time and the work shop manual. well this is what I got.
Attachment 620, Attachment 619

I Just wanted to ask if you think that I can still use the piston and the cylinder head? I need to replace the valves, do u guys know where I can find them?
Thanks for reading, I would really appreciate any comments.

Just my opinion but it appears that a valve let go and beat the living daylights out of the head and piston. That kind of damage could possibly cause hot spots if you re-use them. The piston and head could also be weaked through the rough treatment. Have you rotated the crank to bring the piston down to see if the cylinder wall was scarred? Others will be along soon with more ideas and opinions.

Dang :(

Can't really offer any opinions on the re-usability of the parts, but good luck.