Yes, I noticed the setup you advise in this forum earlier, but was quite happy with my setup and wasnt sure that stock needle and large jet could be much better.
Right now the carb is removed and it will be easy to do some experiments.
Will let you know about results

 

I am aware, that over the years, this stuff has become"second nature" to me while still a "black art" to most - but it really isn't difficult to understand and utilize the basics, the process of successfully achieving best CVK performance in a lidless KLX application. For those with lids and/or snorkels, I don't have data for proper main jet sizing, but the basics still apply.

1. Max power requires the proper main jet for RPM's above 6k - and this is the most important goal - miss this goal and you've lost the game regardless of what else you do. Get the correct main jet first - then never touch it again because if you do, you lose the game again..
2. The correct main jet must be controlled / muzzled / kept in check - during mid-range ops. This is done with the proper needle, proper clip setting on the needle, proper slide spring, and proper slide lift port. Fail to do this correctly and you'll have a grossly overfueled 3.5k - 7k rpm range. Do this right and you have won the game - and you've got a whole new bike..

We are actually very lucky in that the stock slide spring, stock slide lift port, and stock needle, will adequately control the huge main jets required for some KLX lidless combos. Also, the DJ needles (at 1N only) will create different fueling below 7k rpm in order to "tune" proper fueling in most lidless applications..

As those that, over the years, have followed my dyno created recipes will tell you, you can't imagine the huge increase in power you get from doing this stuff right. You have to feel it to believe it..

 

So, I did some experiments, not very lucky so far
Changed N1TC needle back to to the stock one.
Changed 132 main jet to the biggest I have, 162. To be honest I must say these are not Kawasaki jets, I have a set of chinese jets from aliexpress. But I believe they are close to Kawasaki jets numbering.
It was more difficult to start the bike than with previuos carb setup, and it was too rich, never saw so black exhaust gases before. Very unstable and dying rpms at idle...
Then changed main jet to 148, also tried to set the pilot screw from 2.5 to 1.5 turns out, but anyway it was too rich.
Ride some circles around the house, maybe the performance is a bit better but definitely something is wrong. Enough for today, will go to have some beer.
Please let me know if you have any good idea.

 

Yes, there is something wrong... So here's some stuff you need to know.

Starting and idling have nothing to do with the main jet or the needle. Both are fueled entirely by the Pilot circuitry. Any change in starting or idling is a newly created "fault" that must be fixed - and has nothing to do with main jets or needles.. A faulting slide, missing needle jet, etc - from a faulty reinstall - can cause main/primary circuit fueling to be introduced at idle and other inappropriate times, serious flooding will ensue..

I only know DynoJet jets and Keihin jets built for the CVK34 carb - using something else with unknown flow characteristics is "shooting in the dark".. For instance, when you look on the conversion chart on my signature line, you see that mikuni jets have a radically different numbering system - a M148 = K176 !!!!!

You've not shared what exhaust system components you are using..?

You will need to make sure you are using the stock slide spring. The DJ spring is too weak on a lidless 250, and useless on a lidless 351 - It'll cause midrange over-fueling..

Your lift port (hole in the slide that allows engine vacuum to lift the slide) needs to be the stock .1" - if drilled oversize (usually to 7/64) , you will need to JB weld it up and redrill carefully with a 5/64 bit.. Oversize lift ports cause midrange overfueling in lidless applications..

Perhaps once the issue that has caused difficult starting and idle problems is fixed, one of your Chinese jets + stock needle will "awaken" your bike.. When I say awaken, I mean you'd better have a really good grip on the bars before nailing WOT, it's gonna do stuff you've never seen or felt before as it revs past 6k rpm....

 

The bike is a little cold blooded. Needs to warm up good before taking much throttle, so it is a reasonable idea that it is still jetted lean. I already put the stock slide spring in and have an untried JD144 main sitting in my tool box, I will pop that in and see what happens.

 

Ok Snap.. Going 1N is the key to maintaining your mpg's and a "crisp" midrange.. After these items are done (DJ144, clip on 1N), the #35 pilot is your next issue to address. - Go to a #40, which'll give you full control of idle mixture (AFR) and stronger throttle responses..

Your results should be a noticeable "boost" everywhere - But realize that the stock header is likely to run out of breath (mute power output) earlier than with a stockbore (which it muzzles starting at 9k rpm)..

If you like what you get, perhaps think about a DJ148 for a future trial..

 

All you 351'ers need to know that I am making educated guesses on recommended carb setups based on a "351 CVK test thread" we started and never finished.. The relationship between spring, and lift port are designed with/for the vacuum signaling of the 250 with a stock airbox. It is sheer luck that this relationship is still effective when going lidless on the 250. The 351 vacuum signaling is sure to be quite stronger than any 250. This, at the very least, would indicate a need for a stronger slide spring to better control midrange fueling..

Let us hope that midrange fueling can be controlled properly enough to allow a proper main jet. Otherwise, yall will be saddled with a tiny main jet to get good midrange fueling but with a very lean and low performance upper 1/2 rpm range..

 

I wasnt able to get good carb setup with stock needle (N5AV) and large jet, changed back to the previous setup.
I have stock slide spring, drilled lift port (diameter ~3mm or ~0.12 inches), stock exhaust header, performance slip-on.
Tried temporary solution to reduce lift port by a half, no difference, it's too rich. I'm quite sure that everything is Ok with the carb, and the problem is because of large jet. There is something beyond my knowledge...
So, changed back to N1TC needle and to 132 main jet and bike runs fine again. Actually I'm quite happy with this setup.

 

Ok..
With unknown jets, there is no way to know..In fact, if the 132 you are using is Chinese, it may flow similar to big Keihin and DJ jets as well..

 

Long story short - I was wrong, Klxster was right
The bike had unstable rpms also with my carb setup, after few desperate days found stupid carb assembly mistake.
With stock needle and chinese 162 main jet (which I believe is very close to Keihin 162 size) bike runs fine.
It was the first ride today with properly assembled carb, impressions are that the bike doesnt have much more power but the engine works more even or more mildly, sorry my English is not good enough to descibe it precisely
Maybe it could be better with DJ needle, but it's quite expensive to get DJ kit to Europe...
Will continue testing with this carb setup, so far it seems good