someone please help me

hello all, my son has a king quad 300 after about a 4hrs of riding it stalled on him. when he pressed the start button the lights went out and it started to turn over and just clicked. after releasing button the lights came back on. any ideas of what i should look at??? need to fix it quickly as we are going on vacation. thanks pat

Maybe blew a cell in battery and volts are droppin bad when using the starter

Charge and check the battery, Check pos and neg cables make sure they are on good. check the starting solonoid,