My first round of mods included a 2009 KLX250 DJ kit, 2-Bros. M7 exhaust and all the free mods. As suggested in the DJ instructions, I have the clip in the 3rd position from top, 128 main, A/F screw out 3 turns and the stock pilot jet - I think it is a 35. The bike runs really good. I get some backfire popping on deceleration but overall the performance is much better than stock. However, I am only getting about 82 mph out of it WOT. After some very informative PM's with WestOz and the original advice of 09KLXOwner here is my next attempt:

DJ KLX300 kit (for the needle)
Main Jet 132
Needle 3rd notch from top
Pilot 38
A/F screw 2 1/2 turns out

I also picked up a 130 main jet to experiment with. I ride anywhere from sea level to 2000 feet.

I just received the DJ KLX300 jet kit and the needle is considerably different than the needle in the 09 KLX250S kit. I'll take a picture of them both side-by-side and post it for future reference. I'll probably drill the slide and go back to the stock spring. If the new 300 needle works as expected, I'll send the 09 kit back. I can take a picture and measure the spring length of the 09 kit if anyone is interested.

Thanks everyone for all the help. I've learned so much the past couple of weeks simply by reading the posts on this forum.

 

hehe, I hate to say it but I told ya so. The '09 kit's needle is geared more for on-road performing and emissions. The 300 kit is for a built for off-road only motorcycle and thus is the reason the 300 kit gives the 300 more power than the 250S kit does to the 250S. it's right there on DJ's website. With so many people braggin the DJ 300 needle up to me before I bought the kit myself, I'm a bit shocked to see the dissent now that I'm supporting it. TBH though, I wouldn't care if I had the N1TC or the DJ300 needle in. I can't tell a difference tbh. btw, doesn't DJ recommened 2.5 turns out on the a/f screw? or is 3 with the '09 kit?

 

Now that is funny.
You hate to say it?
IG, you live to say "I told ya so".

(Sorry Deej but if it's teed up nice and I'm holding a driver, I going hit it)

 

yeah, but I wasn't trying to be a jerk about it. I've always said the two needles would be different in the 300/'09 kits. there's the proof. what's with the checking in with deej?

 

09KLXOwner, you fully deserve that "I told you so". Let's see, you suggested the Twin Air or UNI, I picked up a K&N. You suggested the 300 kit, I picked up the 2009 250 kit. What's going in my bike now? A UNI and the 300 kit. Ignorance is bliss... LOL!

BTW, the DJ 2009 kit recommends 3 turns on the A/F screw and the 300 kit recommends 2 1/2.

 

IMO the DJ 250 needle is probably designed to deliver the correct AF ratio to 250cc of combustion chamber. The DJ 300 needle, for 300cc of combustion chamber. (In theory 300cc requires 20% more than 250cc.) The dynamics are not that simple, but there is definitely a basis for a separate design.

 

I ordered the 300 kit today as the dealer near me had nothing in the way of stock keihn carb jets in stock, I also picked up a twin air filter and in a while I will get a muzzy exhaust. this november I will rip it apart.

 

"Seriously, do it, do it.........Do it!"
http://www.youtube.com/watch?v=JoqDY...eature=related

 

how can you say that when different elevations aren't even considered? if earth were flat, your statement would hold merit. but it ain't, and it don't. if your thesis were true, the needle wouldn't be adjustable, neither one.

 

The KLX300 Dynojet needle provides significantly better performance. I've done a bunch of tests with both kits and I'm sold on the 300. I rode for a week with the 250 DJ kit installed and really liked it. Over the weekend I installed the 300 kit and I notice much more pull in the mid-range. However, what I lost from the 250 kit was what I considered a really good throttle response. I think it was due to the shorter spring in that kit. When I installed the 300 kit, I drilled the slide and put the stock spring back in. The bike didn't feel nearly as responsive. Since I had the two kits in hand and really had nothing to lose, I decided to try the shorter spring in combination with the drilled slide. I figured, what's the worst that can happen? The slide won't close properly or I might get oscillation - all easily remedied with the kill switch and I can go back to the stock spring. I put in the shorter spring and fired the bike up. Normal idle so I blipped the throttle a couple of times. Seemed fine. Time for a road test. Out on the road the excellent throttle response was back! Deceleration was fine, no oscillation when holding a steady speed. No problems whatsoever. I love the throttle response and after a full hour of riding I've seen absolutely no adverse effects to running the shorter spring with the drilled slide - just improved throttle response. I'm going to leave it in. I've included a couple of comparison pics.