with my 12" stretched zx14, i have to set the chain to be as tight as a guitar string, otherwise it flops around and beats up the bottom of the swingarm badly. tbf, i've got hundreds of runs on it and the countershaft seal doesn't leak so much as a sweat: indicating that the countershaft bearings are handling that extreme chain tension well. this year i'm adding a chain roller to the underside of the swingarm, is as somewhat common with pro street bikes, fwiw.