Hello everyone. First of all, I would like to apologize for the mistakes in writing, because my English is not the best, because I am helping myself with the google translator.
I'm glad I found this forum, it helped me a lot. Now I have to ask a question.

Yesterday, under high revs, both valves broke at the top of the head where the spark plug is, it is a little damaged or can it be restored and sanded down, below if I want I will attach two pictures of what happened. The exhaust valve suffered the most because it was actually twisted. Thank you greetings from Slovenia to everyone for your effort and your answers

 

If there are no cracks in the head, and valve seats are OK, you can re-use the head. Check the valve guides are not cracked or broken, and replace them if they are. Remove the piston and check the underside for cracks. If it is not cracked, and is not nipping the rings, or scored you can re-use that too.

 

thanks for the quick reply, now I opened the valve cover and came across these small cracks, I don't know if this is correct or not, under number 1 I marked that it is not original, I know number 2, but I don't know if it is original or not, that it is a hole, so I am attaching one picture from of the valve cover, which shows a small crack next to it, I will add 2 pictures of the cylinder, thanks again

 

I can't tell much from pictures, only you can judge if the cracks are going to cause problems with leaking oil and compression. The cylinder has had moisture in it, causing a bit of rust, but I recon that when you hone it, it will come up good enough to re-use.