I bought a 1991 4x4 bayou 300 in non running condition a few weeks ago and when i went to fire it i could hear and feel air escaping from around the spark plug. I took and out and when i put it back in again there were enough threads for it to go in but once it bottomed out it kept spinning. I took the head off cause i figured i would install a helicoil, but i noticed that the spark plug hole is awfully close to the valves (see attached pictures). Im afraid that if i helicoil it, the enlarged tap will take out material from around the valve seat and ruin the head. Also i noticed that at top dead center i can put my fingers on the piston and rock it ever so slightly back in forth, it doesnt make any noise when i do i dont think its hitting the cylinder wall. The cylinder itself is still smooth with no visible scratches but i cannot see the crosshatch anymore. Does this mean i need a top end or is it pretty normal for an older machine? Ive never seen it run so i dont know if it burns oil, and theres no hour meter on it.

Im more concerned with the spark plug hole, how do yall think i should go about fixing it?
This is only the second quad ive ever worked on and its the first time ive had to remove a head. Any advice or suggestions are greatly appreciated.
Thank you for reading