I still have the orignal pet cock on one of my k5 and it turns ok ,it might just need some tlc . With out going over to the work shop and start to swap parts im sure a later model pet cock , which are easier to turn will fit, i use a klx 110 pet cock on my kdx200 h for other reasons , it fits no dramas . i do know the steel tank kdx200 adr model pet cock will not fit any plastic kx , kdx ,klx tank. kawasaki are good for interchange ability between old and new models.There a few things to look out for on k5 but if you study this forum you be fine .