Hi everyone. I just bought me my rebuilt '77 KZ650. I have been have issues adjusting my carbs' air/fuel mix. Running a 4 in 1 with aftermarket exaust and pod filters.
I got the bike with 102.5 main jets and just changed to 105. Standard pilot jets I believe but the bike is still bogging and losing power when I open up the throttle to a certain point. Any help??
I think you will need a larger main jet. I usually suggest as a starting point for the vm24ss carbs on a kz650 when changing to pods and 4 into 1 exhaust to use a 110 main and a 17.5 pilot jet. Keep in mind that this is a starting point and you may find you need a smaller or larger main than what I suggest.
Here are some general guidelines (note I said general) for jetting changes on round slide Minuki carbs when changing intake air filters and exhaust.
1 jet size for pod (K&N, Uni, generic) filter (single inside the air box)
1 jet size for drilling out the bottom of the air box
2 jet sizes for both single K&N and drilled air box
2 jet sizes for individual pod filters
2 jet sizes for 4 into 1 exhaust
1 pilot jet size for every 3 main jet size increase
Add up all the jet size increases and subtract one. (Remember they go in steps of 2.5 for each jet size).
Under a mismatch condition, like individual filters and stock exhaust or 4 into 1 header with stock filter and air box, subtract an additional 1 jet size.
Check plug color often, sync carbs after each jet change, make sure the floats are set correctly.
Make sure your carbs are in perfect working order before making jet changes.
Stock main jets: 102.5
Stock pilot jets: 15
2 sizes for 4 into 1 exhaust
2 size for pod filters
Main Jet Calculation = (2+2) - 1 = 3 size main jet increase or 102.5 + (2.5 * 3) = 110
Pilot Jet Calculation = 1 size pilot jet increase or 15 + (2.5 * 1) = 17.5
Another question is whether or not I should adjust the needle setting and what determines that?
The bogging starts when I turn my throttle relatively wide. It starts soon if i snap on it but if I ease in to it the bogging starts around full throttle in every gear
I have installed the 110 main jets and seen significant performance increase when I open the pilot jets on half way (hesitant to close them any further). It is still bogging but only in high gear when there's less torque involved I'm assuming. Still waiting for my 17.5 pilot jets. Will they allow me to restrict more air?