Carb help please !

I have searched thru the older post and still confused
My KZ650B2 has stock airbox and last year installed a Kerker 4 into 1 my carbs are running terrible this year and need cleaning Im thinking since I will have them apart may as well re jet in order to run smoother when I changed the stock exhaust it ran okay with a slight hesitation and harder starting when cold is their any rule of thumb I can use to help my situation? This Old guy would be very appreciative with any help you can give me. Thanks Rob

The cleaning will do more good than rejetting. If you have a 4 into 1, shouldn't need much changing of jet sizes. The slight hesitation is more related to pilot circuit and that circuit normally is in dire need of cleaning. I would replace the pilot jets. Tell me what your current jetting is, and maybe I can help.