After doing the MCM, and jetting the bike with the 2125 kit, the bike has developed a miss or sputter between 6000 and 7000rpm.
I could sorta feel something when the bike was stock, but I thought it was my imagination/the stock jetting.

Current jetting: 120 main, 3rd notch on DJ needle, air fuel screw 2.5 turns.

If I wack the throttle wide open, it pulls like crazy. Any throttle snaps below 1/2 throttle are fine. Low speed, high rpm, you name it. No problemo. I can hold the bike and cruise at 5000rpm as well.

Once it's over 6000, the problems appear. I can back the throttle off and hold it at about 5/8th of a full turn and the bike will bog or sputter. Lower gears are no problem, the feeling is pronounced mostly in 4th and 5th.

I pulled the needle, checked the spring, washers are on top of clip... no pinholes in membrane etc. It will rev right pass the flat spot but if you want to make it happen, it's easy to do. Almost like a button is pushed to make it run like ****.

There's alot of good information regarding the rectifier ground wire, but my 2007 klx250s doesn't have the same rectifier. This shouldn't make a difference though, if it's the ground itself that is the issue.

I chased the black wire with the yellow stripe, and if connects in a loom up under the seat. I don't have any inline taps or solder, so for now I can't add a ground. (going to hardware store tonight)

I also couldn't find anyone with a Gen 1 Klx250s posting about the "stumble at 6500rpm" maybe I'm the first one! (lucky me.........)

Has anyone else had this problem on a Gen 1?

 

When I did MCM with stock bore, I found it was happier with richer main jet than prior to MCM. A bigger pilot helped to tune out the low throttle opening cruise stumbling/hesitation. There is a great google docs setup sheet that you can reference to see where you need to be with your setup.

 

When you get to that sputtering range, pull the enrichener (aka choke) out and see if it sputters worse or starts to clear out a bit. The enrichener circuit will slightly richen the mix, so if it sputters worse it is too rich on the needle and/or main if it starts to smooth out it is lean on the needle and/or main. Your 120 is about the same as the Kiehin 128, a common jet for mostly stock set up. A header might need bigger. The stock set up also goes 2nd groove from the top on the needle, when measured apparently the Kiehin and Dyno Jet needle are similar so you might be a bit fat there. But at 6000 I'm thinking main jet.

I will say you need to give KLXter a call on this one, he knows the Dyno Jet stuff.

 

The choke idea is one I forgot to try the other day. I'll give that a shot before running the ground wire. I was su****ious of being too rich, but at sea level and in the winter... the o2 content in the air should be at it's highest. Maybe it's not rich enough! Didn't clear up when I moved the needle from 3rd notch to 2nd, so it's not too rich, at least on the needle.

thanks for the feedback 2veedubs, it could very well be too lean.

Klx678, remember that I'm running the Dial A Jet too. Either it's not working, or it can't correct the the bike being that lean. Would you suggest turning the dial up on the dial a jet before changing the main? I left it in the middle position as you suggested and as is recommended from the instruction manual.

 

Pulling the choke did the trick.

Now I'm really wondering why my snake oil device isn't working :P

I specifically put a smaller main jet in, to allow the Dial a Jet to work properly.

If it is a lean spot, why wouldn't the dial a jet add fuel to the carb? Faulty or out of range?

At least if I go for a bigger main and it's too rich, the dial a jet will do nothing... so might as well ramp it up.

 

Just for your knowledge you keep saying Gen 1 but you have a 2007. Gen 1 would be the 1979 KLX250

 

Call Phil at Thunder Products, tell him what's cooking. I am running stock pipe and I know running the TC-N1 on 2nd notch and the 125 are on the edge of lean, I had done the choke trick when I was getting surging with a shimmed stock needle, causing me to switch to the adjustable one. I also had the slide bleed hole drilled to 7/64". If you have a header (I forget) it may still be on the edge of lean. Either way, I'd call Thunder Products and talk to them.

 

MaverickAus, I see what you are getting at but I have to disagree. I am referring to a gen1 klx250s, which is different from the bike you pictured. The klx250s is closer to the klr250 than the old klx250 you are referencing.

Also, I only started saying gen1 after reading it on this forum. Have you attempted to correct others on this or am I the first one?

https://www.kawasakiforums.com/forum...erences-37329/

https://www.kawasakiforums.com/forum...-brakes-42923/



Klx678, I have the stock header and stock exhaust. Last night I took the carb apart again, and noticed the slide bleed hole seemed a bit bigger than I remember from my '09. Sure as **** it's just under 3mm (7/64th's) wide. The PO must have drilled it.

Learning this, I put the stock spring back in. I didn't want to add another variable to the mix, although I've read about people drilling the slide and using the DJ spring "with no issues".....

I tested the carb by blowing air into the slot above the inlet side of the carb. The slide goes up and down smoothly, and the needle is sitting in the proper position with the washers on top. Jet nozzle installed properly, diaphragm seated properly, float level set to 17mm.

Installed the 124 main jet, set the DJ needle back to 3rd notch. Bike pulled better at 3rd notch from top vs 2nd notch from top, but that might have been from the main being too small. If this is the case, it's not as hard to change a needle clip as it is to change a main jet :/

If bumping up the main doesn't solve the issue, I'll be sad. Fingers crossed!

 

I am extremely happy to report no unusual behavior coming from the bike. Starts fine, runs great. The 124 main jet is clearly doing something. Clean smooth power delivery and really nice feel when cruising along. No sputtering, hesitation, or anything like that. I can hold the throttle at any position and rpm and it just pulls along.

Seeing as how I set out on this mission with the sole intent of making the bike a little bit more powerful while maintaining the OEM muffler.. the gains made are outstanding.

I really do encourage anyone to try jetting and MCM with stock exhaust before spending the $$$ on a full slip on.

Thanks for all the help. Now onto better things... like seat covers and aux lighting!