kz1000 jetting questions

Hello I have an 81 kz1000j with 4 into 1 exhaust and stock mikuni carbs 127.5 main jets and 37.5 pilots (standard stock jetting i believe) and K&N pod filters

whenever i am at about 2500 to 3000 rpm the engine seems to sputter and misfire and the whole bike kind of loses power and like a cylinder is missing and then lurches violently as it catches again (not cool) Anything higher than that and it seems to run ok, also, the hotter it is out and the hotter the bike is, the worse it gets, and at a wider rpm range,

I have checked my coils and plugs and i am getting good spark , though my plugs seem a bit too light colored like im running lean. So I tried to adjust the pilot screws but (between carb body and engine) but they didnt seem to have enough range to do anything:(

I think i need to step up my jets but i have never rejetted carbs before and am a little lost as to what sizes i need, I was told to try 133 mains and leave the pilots as they are, does anyone have any advice? can you just change the main jets without changing the pilots?

I just lifted my needles one notch tonight and i will try running the bike tommorow before any jet changes

that is the mid range and it is contrled by the needles so you are going after the right area but it might also need a bit bigger main jet so keep playing if you raised the needle [lowered the clip ] then you are riching up the mid range which it sounds like it needs. yes you can change the mains without the pilots. with that 4-1 and pods you will definitly have to richen things up a bit.

Yeah ive got the 133 jets to try out after


How does 4 into 1 affect your carb mixture? Ive never really understood how that works, I think i would like to change to dual exhaust but thats just a pipe dream:laugh: