The design of the DJ needles were created for very specific applications - none of which apply to a 351 or even a "fully uncorked" KLX250..

DNO352 is for a lidless KLX300R with stock exhaust. (But includes a DJ132 main jet for use when the silencer end cap is removed.)
DNO228 is for a KLX250 with stock exhaust and airbox - with alternative settings for use if the snorkel is removed.

Thankfully, each needle can be effective when used with a stock slide spring and stock slide lift port. The DNO352 will more effectively control midrange fueling, but the aggressive "tip taper" will cause problems with drilled lift ports or weaker slide springs. The DNO228 will cause midrange overfueling with drilled lift ports and/or weaker slide springs..

This thread may help you ascertain the fueling curves the DJ needles create.
https://www.kawasakiforums.com/forum...urments-43117/

If you want to alter your midrange fueling, your best method is by shimming the stock needle shorter with the DJ needle washers, or similar, placed under the needle retainer.

 

So I finally slapped in the DJ144-1N and the bike does run with more torque. Throttle only just lifts the front wheel off the pavement where it would not with DJ140-2N snapping open the throttle at about 2000rpm in 1st gear. No other changes made. I have to hold onto the bars a little more than I am used to. It probably doesn't help the power wheelies that I run 15x39 sprockets with a taller 130/80-17 rear wheel. Also recently slacked off on rear spring preload to get sag around 33% instead of 20% like I have been running. Potholes are a bit softer now. Overall the new jetting feels good. Will have to wait and see on the fuel economy. My last tank was 73 mpg, last several have been over 70.
Edit: an extra good thing is that my low rpm torque and smoothness improved; engine pulls much more smoothly from 3-4krpm where it used to sputter and buck until around 4krpm in higher gears. I can now cruise 35mph in 6th gear where it needed to be in 5th before.
Edit: 1st tank of gas got 71 mpg, nice.

 

Ok, that is expected results.. If you are really still running the #35 pilot jet, a move to the #40 should give you noticeably more powerful responses to quick throttle changes and snaps.. The #35 is too lean for stockbores !

You know that the reason you have more power now, is because your engine is being fueled more correctly than before.

After careful, scientific, and controlled MPG measurements are made at an RPM target somewhere above 7k, a change to a DJ148 and a MPG test repeat should show whether the upper RPM range needs more fuel or not.

Or take her in for a quick dyno test to get the power curves and the fueling curve..

 

Best mod I did to the CV other than jetting was changing to a single cable two stroke throttle. Used a Magura 314 which you can set for MX (quick pull) or Enduro (slower pull). I did it because the stock street bike throttle is so slow compared to my other dirt bike effecting wrist position when you need a handful. An unexpected but pleasing side effect was an impressive increase in throttle response out of the cv making me forget changing the carb for a pumper. You wouldn't think it'd make much difference but it did, no problem lofting the wheel without clutching for suprise log coming around the corner.

 

That's interesting.
Does anyone else have made this mod?
What about the throttle cable, can you use original one or need to replace to some other?

 

I just modified the carb end to give me a quicker pull. You can also change the throttle tube with stock setup, there is a few ways to do it.
Definitely needed on this bike IMHO , had to adjust my grip to get to WOT before the change

 

I checked the throttle on my bike, which I believe is original Kawa part #46019-1093, and found that the throttle angle is 1/4 or ~90 degrees.
Magura 314 is adjustable throttle from 90 to 100 degrees. So, there is no real difference...
My KLX is older 2001 model
Could it be that newer bikes have wider (180 degrees?) throttle angle?

 

 

Ok, since MPG have stayed the same, you are free to try a DJ148 main jet. A "two bumps up" approach saves tremendous time - dyno results shows a one-bump (DJ146 in your case) is a negligible change to a KLX fueling curve..

Here is how this works: As long as MPG's hold - in a carefully monitored high RPM mileage test - you are creating same power with smaller throttle & slide openings. By increasing your main jet sizing, you are zeroing in on proper fueling - Proper fueling, when using a proper CVK setup, will create max power as well as max MPG..

The above testing and conclusions apply to Snappsters engine with its' current CVK setup. He is running a "best choice" setup in his CVK. His fueling for all throttle/slide positions below WOT is being controlled as well as we can control it - short of installing custom slide springs and creating custom slide lift ports.. Mismatched mod combos are not able to create both great MPG and max power..

 

Snappster, getting you to further mod your bike is like pulling teeth..

If your Leo Vince X3 is not, and can not, use a gasket at the midpipe-to-header joint - how bout looking into this header:
- DELTA - EXHAUST SYSTEM