’92 fourtrax TRX 300 Ignition Issues

Hi everyone, first time poster.
I have started collecting older atv’s and fixing them up. My current project is a ’92 fourtrax trx 300. at this stage it runs and drives well but stalls out without warning, sometimes when idling, sometimes mid-ride. it then starts right up again and goes. no amount of throttle when it begins to stall brings it back to life. where should i start my trouble-shooting?
another question which may or may not be related, the spark plug for this quad has threaded terminal. it does not snap on like the traditional rounded terminals such as on a car or truck. my spark plug wire/boot just kinda sits on there. does this mean the terminal connector inside the wire/boot is damaged? shouldn’t it snap on?
looking forward to hearing what everyone has to say.
thanks