Go kart clutch problems?

i have a go kart and the driveshaft is horizontal v shaped and it has no key and i need to find a centrifugal chain clutch that fits on that driveshaft. i bought a clutch but it had a grove (key) in it that wouldnt let it fit on the driveshaft so now im really confused cause every clutch seems to have a key. i have a honda gc 160 5 hp. so if anyone knows of a clutch that will work on it that would help ALOT.