Just wanted to give a heads-up on what jetting has worked best for me so far for future reference. KLXster helped me out with troubleshooting and tips (he's at same elevation and in same area).

I have a 06 KLX250S with the KLX300 Header and Exhaust pipe. "Buttplug" wasn't included, so I use the 3D CNC exhaust tip you get off eBay (only one I've ever seen there). Air filter is a Twinair foam filter. Airbox lid is off.

EDIT - I'm using the DJ 2206 kit for the KLX300 where you drill out the slide (not the one with the spring).

I'm running a #40 pilot, 136 DynoJet Main, DJ needle with clip on 4th notch, and float bowl height should be right in middle of spec (17mm, spec is 17mm +- 2mm). My Kouba fuel/air screw is out a little over 1 turn. Not sure if it's completely dialed in yet, but it's somewhere close.

Has noticeable increase in pull and no bog compared to previous owner's setup (#45!!! pilot jet, N1TC needle on 4th notch, 126 main jet).

Going to 5th notch on clip greatly over-richened the bike... I'd recommend going 5th if using a smaller pilot jet, though (or maybe if float height is different).

I'm not 100% positive on float bowl measurement as it's hard to tell exactly when spring starts to compress, but I believe it's 17mm. I did do the clear fuel line trick, too, and fuel seems to line up with gasket surface as well.

I would say that #38 pilot may be ideal for me (so I can back out fuel/air screw a bit more), but #40 seems to be good for now and would probably be perfect for those even closer to sea level. I'm at 600' elevation.

Non-jetting additional modifications in case anyone is curious:

• IMS foot pegs
• Lowered brake pedal and having the return spring hook through an extra keyring to keep height a little lower (brake pedal placement is only complaint I have with this bike's ergonomics when wearing MX boots)
• Put in KLX300 .46 rate fork springs. Did use PVC spacers but they sounded off (squeaked a lot, probably not completely level), now use small metal spacer that was included with springs. Probably need to re-make bigger spacers but current solution is within spec.
• Put on black UFO fork guards for KX125/250 to replace brittle white OEM ones
• Put on Polysport(?) black fender with extra ventilation. Put in some weird stepped spacers on mount area to give extra clearance between clutch cable and fender to prevent rubbing.
• Put on KLX300 clutch cable. It's supposedly shorter than 06/07 KLX250S clutch cables but the one I ordered sure didn't seem like it... or maybe PO had wrong clutch cable on it
• Unabiker rad guards (now with side panels removed)
• Acerbis green gas tank (does not match my OEM green unfortunately) - necessary as previous 2 OEM tanks either had holes or rust...
• 13/47 sprockets, new chain
• Re-greased/replaced all bearings except front wheel and steering stem (next maintenance project)
• used 98 navy blue/purplish KLX300 seat so I can scuff it up and not worry about it... actually like the way it looks better as well (no clashing green between seat lime green and Acerbis tank).
• Various cheapo luggage/bag options I've tried. So far, best solution has been a $20 backpack on clearance from Motorcycle superstore bungee-corded to area where OEM toolbag was.
• KLX300 dogbones to replace the 2" lowering links previous owner used
• Richocet skidplate
• Kreiger's manual cam chain tensioner

And PO already had acerbis handguards and bar risers on it.

Some rushed pics... have some better pics on my other computer:
Imgur

 

There are some real differences with Zeno's setup. He is using the DJ #2206 jet kit (97-07 KLX300), which is different than the #2152 (09-14 KLX250) - It has no slide spring but has a drill bit to drill the slide lift hole. It has a #0352 needle whereas the 2206 uses a #0228.
It is designed to be used with the lid off - as per instructions.

All-in-all, a very different kit than the 2152. (I used the 2206 kit on my KLX300.)
The needle is, no doubt, much more aggressive than the #0228 and seems to provide a different fuel curve - richer. So good news for 06-08 KLX 250s but no help with 09-14's...

 

Why wouldn't you use it in the 09+ bikes?

 

Well good question - And I haven't researched the matter. Assuming the carbs are identical, and the drilled slide works as well as the spring - that 2206 kit may be superior to 2152 due to the better needle.. My KLX300 runs great with the 2206 I put in years ago but I don't guess I'm gonna pull both bikes apart to check the needle differences.. Perhaps a call to DJ ..? It could be that the 2206 kit is the only way to go for modded 250's - especially when running MCM.. Zeno's experience has me wondering..

 

I think people have used both kits with equal success in any model KLX250. If there's any significant difference in the needle profile, my understanding is that it's relatively small. I think the biggest difference is the spring vs. drilling the slide. It's been awhile since this has come up, but I can't recall anyone with any year model having a problem with either kit. The results and response seemed to be about identical to the point that tuning parameters weren't that different.

 

I am very interested in seeing the differences between 2206 and 2152 kits needles, if any. I guess for more a aggressive the N1TC needle is the way to go. Has anyone tried both DJ and N1TC needles on the same bike?

 

Funny you ask that! The PO had the N1TC needle on this bike. I've tried both N1TC and my DJ 2206 needle.

Unfortunately, the comparison isn't too useful because back when I had the N1TC needle on, I also had the oversized #45 pilot on it from PO as well. The first time I switched out to the DJ2206 needle, I didn't have a screwdriver small enough to remove that oversized pilot jet. So both tests the bike was running way too rich. I remember not feeling much of a difference in performance, and possibly preferring the DJ needle.

Sometime I may have to do another test with N1TC needle now that bike isn't ridiculously over-rich.

 

I'm at 800'. I used the N1TC in my last bike and the DJ kit in my latest KLX. This winter I pulled the DJ kit and went with OEM parts including the N1TC because I wasn't happy with the DJ kit.

 

Oooh! That's basically same altitude. What's your exact carb setup? Pilot, main, notch, etc.

Thanks!

 

Zeno, due to your and a few others' experience, I have a #40 pilot and DJ140 main jet coming.. So more dyno tuning in near future - I'm still trying to get WOT AFR's below 13:1 from idle to 9.5K +..