Ok so I have a 2014 klx250s. I will be putting on a DG-R slip-on, uni-filter, and running lidless at sea level (New Jersey). No MCM for now. I already have all the parts, DJ2152 kit, and Kouba screw. From what I have read, it looks like 40/140 2N is max (but that's with the MCM). Maybe a little rich for me in the midrange?? How much would I be leaving on the table with 38/138 2N and stock cam timing? Does that sound like a good recipe? Will that have a little more flexibility for higher elevations?

 

You seem to have analyzed my DGR charts. Your bike will likely run leaner than mine above 6.5k ( or starting at some point above 6.5k) due to your stock cam timings - since 140/2N already runs at 13:1 on my bike, you certainly don't want to go any leaner on the main jet. Fueling the midrange is a simple clip position change. 2N works perfectly fine sans MCM - but you can always go 1.5N or 1N - which will lean approx 1 AFR point per clip position for all needle controlled fueling operations (about 3.5k to 6.5k @ WOT)..

 

About the pilot jet: Be sure your getting a bigger one for the right reasons. It only controls fueling at idle, very low throttle openings - under 1/4th, assists with transition to needle operations, fuels deceleration, provides for a "accelerator pump" kind of AF "jolt" when the throttle is opened quickly from idle (for bog mitigation)..

The stock #35 will, most assuredly, not give you a rich idle drop - meaning you can turn it all the way to 4 out without it richening up the idle AFR enough to cause a drop in idle speed. If, at 4 out,(and desmogged), you still have decel popping, you will have to get a larger pilot jet to cure it - to richen the decel AFR past what the stock pilot will allow.

Other than fixing decel popping, a 38 or 40 pilot will allow you to fine tune all aspects of pilot circuit operations as noted above. While great for "control freaks" like me, it is certainly not a required mod for anyone who does not have decel popping.

The 140 should be good/perfect up to around 2k ASL - with increasing altitudes, the entire fueling curve(idle to redline) will become increasingly rich with a noticeable effect at some "point" - that "point" is unknown. As I found out on the dyno, KLX's will run perfectly fine with AFR's all the way into the 10's !

 

The pilot circuit never transitions out (never stops supplying fuel) and supplements fuel at all throttle openings. If you go substantially larger, it affects needle and main jet selection. True story.

 

Everyone should research and study the CVK for themselves. The effects on needle and main jet operating AFR from the pilot systems' 3 (tiny) unmetered transition orfices are considered negligible. They are designed to be able to only flow useable AF in high vacuum operations. Meaning operations where the butterfly valve is residing on top or just beyond them. Such as anytime you pop open the throttle from idle - there is a few milliseconds where the butterfly valve uncovers them while vacuum is still high - this momentary high vacuum "sucks" AF out of the 3 tiny transition ports (holes) - So instead of a bog, you get a little AF boost to aid in transition to needle ops.. All other fueling operations (part throttle, full throttle, etc) are low vacuum ops which won't pull meaningful AF from these ports.

But hey, if anyone can show proof that the pilot jet can effectively tune the entire fueling curve, I'd be the first to yell "MY BUTT CRACK HURTS" .. I mean " HALLELUJAH"....

 

The bike is already de-smogged. So you think my first try should be 38/140 1.5N? A 38 pilot tuned mid-way between idle drops should have a nice idle AFR, correct? As in; no soot in the exhaust. ...and still provide a little of that boost you mention between vacuum and throttle. I'd like to see how much the local shop charges for dyno runs. Maybe get a baseline stock first, then the above jetting.

 

I finally finished editing my above post.. I gotta quit doing that..

If you can get a deal to run your bike twice, or more, you would be "Hero of the day" to provide charts for a stock bike.

38/DJ140/1.5N, lidless, with the DGR, will transform your KLX ownership experience.
If soot in the exhaust violates your religion, better sell all those parts (I'll buy the DGR), and run it stock. You can't get proper performance AFR/fueling without it. Every time your runing steady at, say 6.5k RPM, and nail WOT, your uncovering the main jet quickly enough with that DJ spring that AFR's will dip momentarily into the "SOOT ZONE" .. And I challenge you to never nail WOT after you do your mods/carb setup..lol

 

Lol. No religious beliefs broken with a little soot! I just meant it's not gonna run so dirty it fouls up. I had a car once that ran so rich at idle it would leave a little pile of soot on the grass under the exhaust tips. (No kidding!!!) I'm hoping it will run a little cleaner than that. Anyway, I love the smell of unburnt fuel in the morning.

BTW- where can I order a few of those jets? I might as well get 38, 40, 138, 140. Anywhere I can just add to cart?

 

Nope, you call DJ for the jets and the 38 or 40 pilot jet part numbers are in here somewhere..

 

#38 pilot jet 92064-1050
#40 pilot jet 92064-1108