keihin carb jet questions

I have an 82 kz 750 e3, 4-1 Yoshimura race pipe and uni pods, I have been running this setup for 9 years but always had a part throttle lean feeling. I installed a wide band O2 sensor and gauge. I am supper lean on part throttle almost off the scale. It's good from after part throttle up to full throttle. Then I'm way rich. It's got the stick 62 and 125 jets, my question is wouldn't the pilot jet work my part throttle problem? I haven't seen a Kawasaki replacement....... Any ideas or input is welcome. Again the bike rides damn good other then part throttle.

I've always been told to run 70/140 jets when running pods/pipes...

Pilots are hard to come by, at least for my keihin cv34s...

I have seen that set up recommended also, but wouldn't that make even more rich from quarter throttle to full? My problem is just when the throttle is opened.

I'm not seasoned enough in tuning these carbs to say... But I'm sure someone who is will chime in soon enough...

Ed? Scott? Leon?

If you have the full race pipe then you will never be able to tune that lean spot out, it's the pipe not the carbs. I have a full race Kerker KR on my ELR clone with the very same lean spot at partial throttle. Mine is between 3000 and 4000 RPM's, it's not there past 4000 and under 3000. It runs perfect everywhere else. The race pipes are designed for nothing but upper end power not down low. I tried everything to cure the lean spot, went through numerous carburators, CV, VM, RS, CR, ect. Spent a LOT of money and time on carbs and jetting. The best I got was the Mikuni RS36 carbs, they seem to work the best with my setup. Still had a slight lean spot between 3 and 4 thousand RPM but not nearly as noticeable. I would go up on the pilot jet and cure the lean spot but then it would not idle , very sloggy performance and run very rich everywhere else. After years of tuning which also included changing baffle sizes in the pipe I decided to swap the pipe out for a street version 4 into 1 pipe. That solved my problem, lean spot went away but I really liked the look and sound of the old Kerker so I re-installed it and now I just ride it around the lean spot. I came to the conclusion that the problem was the diameter of the head pipes, (huge) that was causing this problem. I have thought about fabbing some inserts for the header tubes and see if that works. Haven't done it yet to busy riding the bike.
I guess the other alternative would be to go to fuel injection.

You should have a lean area right at the slow cruise portion of the throttle. That is how you get decent fuel economy. It should top out around 14:1 while cruising at about 60 mph, holding steady, with the engine fully warmed (riding at least 30 minutes) on a warm day 70 to 80 deg F.

If it's holding steady off scale lean (above 16 or 17 AFR), then it's too lean (or if it's stumbling, it may be too rich to fire, then that gives a false lean reading too, but not likely in that throttle range).

This range is controlled by needle/pilot/slide and even the main can affect it a small amount. Do you have a throttle position marker? This will likely be in the 1/16th to 1/8th throttle position. After about 3/16th throttle the AFR should start to head toward the power range, like 12 to 13 AFR.

Most users end up changing the main to be too rich to help mask the affects of being jetted too lean on part throttle, which is why full throttle ends up too rich.

If you can easily shim the needle, that would be the first option. Most shim washers will be near .5 mm thick. But with an AFR gauge, you can see changes even with .2mm shim changes. Once you get the lean area down to about 13.5 by shimming, then reduce the main (which will hopefully restore the part throttle back to around 14 at the leanest). Getting the needle correct will make you have to compensate on both ends (main and pilot) as the needle affects a wide range.

Some carbs make it difficult to shim the needle, as the extra thickness at the clip binds the needle. Make sure the needle is free to wiggle slightly so it won't bind and grind against the needle jet.

As Baldy said, exhausts will affect this as well, so make sure you have the exhaust you want to keep before spending all the time jetting, or you may have to start over.