Hey guy I'm new here and here is my problem I have a 99 cbr 600f4 bike idles fine but when I twist the throttle it hesitates and acts like it wants to die until I keep trying and get the rpms up to 1500 to 2000 then there is no hesitation only mod on the bike is I put a slip-on exhaust on and went from a 525 chain to a 520 from what a couple ppl has told me it could be the accelerator pump (car term) for the carbs or I need to put bigger jets in but if I remember correctly I believe it still did this with the stock exhaust not sure on that tho