I have sort of a weird problem. The bike seems to backfire on small throttle inputs. If you gently put pressure on the throttle and rev it up to say 1700 or 2000 rpm from idle I get some light backfiring coming from the tailpipe every 1 or 2 seconds. I have the Holeshot 5 degree advancer on there and the carbs are stock with 1 holeshot shim on the needles and screws out 3.25 turns out. I have turned the screws out another 1/4 turn and half a turn but it's too rich. Could it be the timing advancer is screwing up the works? I also had to tape over the Holeshot hole as my petcock died in the middle of jetting and had to go back to stock so I could get it warrentied. So its basically stock but only a tiny bit richer. Once on the throttle the bike has power it just seems that light throttle inputs are a problem. Not smooth at all. More shims maybe?