It would depend on what was wrong with the engine. More details are required.
Weld it.
yes you can. i dont know how.. but you can
purchase a new set
i would say i two stroke because two strokes are much easier to fix, there faster and better.
last guy was a fagayzee so i deleted his post.
It would be more cost effective to replace the blown engine with a re-manufactured one.
Locked meaning blown?,no quick fix.
the easiest way should be to take it and have a shop fix it... or u can buy a new one and put it on yourself
It may have been run without oil and you blew it up.
'''Bring it back to the place you bought it and tell them what happend ...if they can't fix it get a new one'''
odds are if the valve is stuck open it is either bent(from over rev/valve float), or siezed in the guide(over heating). no easy fix sry