New guy here, well not new to motorcycles, just to this forum. Anyway, 24 and been riding for several years, but never had a dual sport type motorcycle. Had quite a few crotch rockets, and a cruiser. Living in Wichita, Ks, and love riding more than pretty much anything right now....except pizza. For the most part loving my 2009 KLX250SF.

Anyway, with all the bikes I've owned and ridden, I've never had to do any kind of performance mods to them. They were either already done, or didn't need any for their purpose. However, with my KLX I not only use it as a fun bike, but as transportation to and from work.

My issues come with a slight sputter between 4500-5500 rpm, and the annoying sound of the whiny exhaust at highway speeds. Also, I was very fortunate one time to get it up to 87mph being in the slipstream of a big Dodge pickup....heading downhill, not really what I'm used to. I know these bikes run lean stock, and I really don't have any other complaints or issues with it, but I want it to be as smooth as possible.

I have ordered several upgrades and have them ready to go. FMF Powerbomb Header (installed), FMF Powercore 4 (installed), Uni Air Filter (pre-fitted, ready for install), and a Dynojet Kit. I don't really understand the way the carbs work, and I'm not wanting to dig into it real deep until I get some help. Normally I'd just take it to a shop, but I'm a little short on $$$ and would like to learn how to work on carbs to save money in the long run.

Really all I'm looking for right now is a generic place to start with the jet kit, and then I can try to fine tune it later. I've been hunting for a KDX snorkel since I use the highway quite a bit, but until I find one I'll be using the stock snorkel and lid.

I've heard about adjusting the exhaust cam, heard about drilling the choke jet out to 0.018" and have been told to run it without the airbox lid. My long term plan (as in over the winter) was to install the 351 kit with the pumper carb, exhaust, and a couple accessories here and there, but I just got tired of the way it was running so I decided to go ahead with the exhaust until I get the money for the big bore.

 

>My issues come with a slight sputter between 4500-5500 rpm

If its remotely like the issue outlined in this thread: https://www.kawasakiforums.com/forum...welcome-43229/ (check for videos in that thread to see example)... I had to change carbs to fix it for me.

You're much better off digging in and learning your own carb than taking to a shop anyway. 95% of shops will just give it a best effort "good enough" approach.

 

Well, if you would run it without the lid, I can get you to around 23 HP.. And with just one "carb wrenching" session.. Through the stock snorkel, you'll have to follow the directions on the 2152 kit..

BTW, if you use the lid (with or without snorkel) you can call DJ for advice..


As far as learning about the CVK.. If you have trouble understanding a particular circuit or function, I or PWJM can answer questions.

 

The sputtering/stumbling - If you do, in fact, have the same symptoms that Snowdrifter and PWJM had, know that there is no explanation or solution at this time. I am running Snowdrifters' "faulty" carb on my bike right now without any issues..

 

PWJM, I had previously read through some pages of that, and while it sounds similar, I'm not sure if it's quite the same issue. Once I get some more free time and I'm not completely drained from work I'll try the wire ground I had seen there. I'll go back through all the pages probably tomorrow and do a little better comparing. I know mine wasn't very consistent, and would seem to only happen in 4 5 or 6.

I would love to learn about carbs, but I don't have anybody to teach me and I try to do too much at once to focus or actually remember anything I learn. I also don't want to just leave my bike in pieces overnight as it is kept outside under an awning. Safe from most of the elements, but most definitely not safe from bugs.

I have heard about serious power gains without the lid, but I also heard that it would be starving for air on the highway as there is no way to force air down to the filter and intake. Most of the riding I do is to/from work ~10 miles each way, along with wherever I decide to go for lunch.

Klxster, who is DJ? I'm half tempted to mold my own lid that has a snorkel, but is much more open than stock, we'll just have to see.

I've seen threads that rejet for a different air filter, and threads that rejet for a new exhaust, but not one for both so I'm not really sure where to begin with the rejet. It has plenty of jets in it, along with a needle, drill bit, spring, and something else I think, but without knowing which parts do what, I don't want to screw it up.

I would like to give a huge thank you to both of you for replying so quickly already. I've had a similar post on ThumperTalk for about a week with several hundred views, but no replies.

 

all you need to know about tuning these carbs is present on these forums it's how I learned!

There's two mainstream methods of running the bike for a slip on and other mods. One is using the DynoJet 2152 Kit which it sounds like you have. The other is using the factory Kawi parts and the N1tC Needle. I've tried both and they both perform very similarly with the DJ needle being a slightly more aggressive fuel curve.

When klxster says DJ, he's refering to DynoJet.

You won't need to worry about leaving your bike in an un-assembled state. I live in an apartment and feel your pain. All my work gets done in the parking lot for all to see. Carb removals for the CVK34 (stock carb) take about 10 - 15 minutes tops. I can do it in 5 or so now. Maybe 30 - 40 your very first time.

The CVK34 is pretty bulletproof and you only really need to take special care with the slide and the float.

If you've got 3 hours of free time, you've got loads of time to pull out the carb, rejet, reneedle and reinstall! Probably time for a test ride too. Once you're quick you can do it multiple times in that time frame!

 

LemonRX, I think I have a feel for where you're at on all this. You're new to all this and you've been misinformed with strange opinions and, at the same time, you are under-informed on the options that you have. So lets get a few things understood - Except for the drill bit in the kit ,(to use on the fuel screw cover), don't "drill" anything on your carb. Also, running without the airbox lid will allow you to achieve maximum power levels out of your exhaust system and Uni filter, when the carb is set up correctly.

Firstly, if you do have the "stumbles" as shown in Snowdrifters' video on PWJMs' thread, there is no known cure. They both have replaced the stock CVK34 with a TM36-68 and report the problem is gone.

If you want to go "by the book" , pull the snorkel, install the kit as per instructions for stage 2. At your elevation, I would go a little "off book" by using the included DJ132 main jet instead of the DJ128 as your exhaust system creates a need for extra fueling up top (7k-10.5k RPM)

If you want to go for maximum power, you can use my dyno tested setup. If you want to go this route, I'll share the best setup I have at this time.

 

I was going to tear it apart and begin working on the carb today, but once I got home from work I got sidetracked and now I'm ready for dinner and bed. Tomorrow I have a dinner date planned, so I'll try to at least get the carb removed if not taken apart before I have to clean up to get food.

Yes I do have the 2152 kit, and I feel stupid for not knowing that DJ meant Dynojet. I've had all the fairings off before and was about to take the tank off to remove the carb, just decided to put them all back on before a storm rolled in. Another reason I don't want to leave my bike disassembled, plus we've been getting some heavy morning dew.

Yes Klxster, that's pretty much where I'm at. My first bike was a 93 Seca II and I had the carbs pulled off to clean them, but never got very far. I think for right now I'll just get the carb adjusted to the exhaust and air filter, then begin playing with the lid and snorkel once I better understand what's going on inside the carb.

After seeing a video of his stumbles, I'm confident that we have different issues. Mine never seemed that bad, and it wouldn't last for that long. I'm thinking it's just jet overlay, like they're not in tune with each other to perform smooth throttle response. Never had an issue when running a constant speed, only when accelerating.

Now before I get into all this, where can I find out what each component of the carb does, and what happens when it's adjusted? I'm unsure on the function of these things. Like what purpose do they serve I guess? Also, what is the difference in adjusting the jets? So if I unscrew the main jet, will it deliver more gas or less, and how will it affect the bike? Similar question with adjusting the floats, and the different notches on the needle.

If you would like to send your setup sheet, that would be awesome. I would love to get maximum power out of this thing, as I plan on turning it into a DRZ killer (they're over populated in this area) but for now I'm using this as a learning experience.

 

Ahh, you're not grasping the whole picture yet.. So lets' change the landscape.

if you are going to run the stock snorkel: You should choose a stage 1 setup - installed as per the instructions.

if you are going to run the lid without the snorkel. You should choose a stage 2 setup - installed as per the instructions. ( In this case, I would use the 132 main jet)

If you choose to go for maximum power levels, you will be running without the lid and should use my best current setup.

So you've got three choices based on how you want to "run" your airbox.. You choose your airbox config first, then the appropriate carb setup.

 

Hmmm....But if I run without the snorkel and lid, then will it still get enough airflow at highway speeds? Or would it matter since it would be running rich instead of lean?