just went for a rip to get gas, as I thought it would be smart to tune it with fresh stuff.

Still not idling properly, have to set the idle screw way out which essentially brings it out of pilot range. Back in the carb I go...

Very happy with the midrange/top out power

 

trust me take the needle back down to 3rd clip

 

3rd clip will get rid of the hiccup and about .5 lb ft of TRQ with AFR spiking up over 15:1 @ WOT.

 

You made 2 changes at once, right? Change one back and see what happens.
Wait, it was 3 changes. Go 3rd clip new needle and old pilot, to start.

I just reread the 1st post. Try a 35 instead of the 38.

 

Great news! I meticulously cleaned and reassembled the carb, ensuring that the float boat was set, needles were clean and everything was moving and sliding as it should. It worked! Runs like a beauty now. The gains are very noticeable, and I no longer have a strange exhaust note while cruising at 5-6000rpm as it had before.

Many thanks to KLXster and others for the hard data and suggestions for improvement.

I strongly suggest anyone else at sea level also do this set up, or at least try it.

*I had tried the needle on the 3rd clip with a 132 main on my 2010 KLX250sf. Only noticed a slight top speed gain no overall power or throttle response changes. Went back to 128, as I wasn't running it without the lid. Never thought at the time to put the clip on the 4th spot with the 132, as it had been too much with the 128 (yes i tried it) The sf was sold last spring. The 2009 KLX250s that I currently own came with a 124 main installed, stock pipe and clip on 3rd position. I put on the FMF pipe and pulled the lid, while installing the 128 main and leaving the clip at 3rd slot. That was of course improvement over the previous owner's set up. I have tried many different jets and combos on two different klx bikes and this new current set up is the best. The 132 main and 4 slot on the clip is worlds above the 128 main with clip on 3rd slot, at my elevation

*Maximus Prime: I changed from a 128 main to a 132 main as well as moving the clip on the needle from 3rd position to 4th position. The problem laid with something else. Cleaning it and carefully reassembling it seemed to do did the trick. Also I don't have the stock pilot as it came with the 38 installed.

 

Your very welcome CC_Rider. I'm trying to spread the word about using the #132/4th notch on "uncorked" bikes near sea level. It is ashamed someone before me years ago didn't dyno test a KLX and find this out.. It is such a big gain that it must be shouted from the roof tops to get everyone " in the know"...


Now, get the MCM done and "feel the power of the force"...lol

 

I'm tempted to run the 132/4th notch combo but I'm worried about 2 things...
1) the reported WOT bog, when I'm in the bush and go WOT I need power now!! That bog could get me into trouble, I had a cr250 that sometimes bogged at WOT, many times that cause me to drop the bike or fail on a hill climb...
2) at sea level this sounds good, except for the WOT bog, what about at 1500 or 2500 feet where I dirt ride?? I care more about performance in the bush versus performance on the street....
Hey CC rider, I'm in Victoria too, we should go for a ride...

 

The bog is really not a bog, it is a instantaneous hiccup - and it is only every now and then , not constant. It is not anything to worry about - I just want anyone who is going 132/4N to know that the periodic hiccup is a possible side effect - I'm all about 100% disclosure.

132/4N at wide open throttle will still be lean - peaking up to about 14.5:1 - near sea level when you analyze my dyno chart.
What this means is that 132/4N has some "built in" higher altitude forgiveness at WOT.
While I have not ridden my bike up higher - CMOTT has taken 132/4N up around 2000ft.

For me, the street performance is cute but I'm an offroader, it's all about lofting front ends over logs and jumps..

The extra power is available to anyone near sea level, with slip-on, no lid, with or without MCM..

Go 132/4N, go ride, if you get so high that the bike runs poorly, pull over and put the needle back to 3N. That will give you even more high altitude forgiveness and most of the power improvement.

 

I would like to mention that the "bog" I reported was probably more due to the lack of fuel going through the pilot circuit... After cleaning and reassembling my carb for the second time, the bog was cleaned up. I rode the bike 35km's both way to work and can't feel any problems, aside from my loose chain

My gearing is 14/39, I can't imagine what sort of kick this would have down low with a few more teeth on the back :P

P.s. I've topped it out at 146km/h (indicated, not proven) with these gears.. And that was with 128/3n

 

So following your suggestion, I set my bike up with the same carb settings, using the DJ kit. It's far richer than my 07 was (125 or 128 Kiehin jet/KLX300 needle 3rd slot), and I thought it ran very well.

I took it out Saturday for a ride, and was really underwhelmed by the power. It was lazy on top, and really weak in the middle. It felt like it could have been either lean or rich, so I was prepared to make a few adjustments. Then I got the idea (ok, I was lazy) to put the lid back on and see what that did. Went out for a rip, and it was much better. It felt like I had expected. Lot's of pull, and it actually wanted to rev.

So now I have to figure out why. I have the backfire screen out, K&N filter, 800 ft and it was about 55 degrees.