I just picked up a 2013 KLX250S with no performance mods. It sat for a year, started, but didn't run well, so I've been through the carb and got it running back to stock form (looked clean, just a bit of clogging in the main and pilot). I also put a new plug and new unifilter air filter in.

I've been through many posts here (thanks @Klxster and others), my questions are related to order of mods and recommended setup. Feel free to point me to any specific threads.

1. I plan to get a new exhaust. Is Barkers the best route if I don't mind the $$? It looks like a comparable spend to FMF slip on + header. I don't want it super loud and will run a spark arrestor. If I get Barkers I'll go through B&B for what he's done for the klx community.

2. To allow carb tuning, I was thinking of getting the exhaust with an O2 bung so I can get a standalone air fuel ratio monitor to allow for later jet & screw tuning based on what I see riding. Anyone done this? Did it work well? I'll probably go with a wide band kit (~$150) instead of narrow band and volt meter setup. Is the location of the O2 sensor just behind the passenger peg optimal or is in the header better?

3. I plan to get a DJ jet kit. It looks like the 2152 is what's mainly used and the 2206 can be used (I believe it has larger jets?), for full after market exhaust and airbox (see #4) mods should I go with the 2152 or the 2206? I live in NV around 2,000 ft elevation, but will ride between -200 and probably 7000 feet out in death valley, so I'm thinking the 2152 should be okay. I've seen Klxster's very good post that's sticky on the form page, so that will be my baseline if no one has other thoughts on it, like DJ spring vs stock spring, etc.

4. For the airbox, I'll probably 3d print my own cover and open it way up, but not quite lidless, maybe with some snorkels I can tune. This will allow me to play with getting the air flow right. For recommendations assume it will be lidless since that's a known quantity.

5. Would you drop a tooth on the counter sprocket or stick with stock? I'll be doing desert riding with washes, climbs, and some more open higher speed areas and some roads in between.

6. I don't plan to do the MCM, at least not right away.

7. I may eventually put a 351 kit in, but think with mods the 250 may be fine for what I'm doing (I have a bigger adv bike for if I want gobs of HP). But I do want to line things up if I go that direction.

8. What order would you do the mods in to avoid ordering both jet kits or just make things easier? Would you do the initial DJ jetting first (2152) and get running peak and then do the exhaust? Or do the exhaust and jump to the 2152 stage 2ish per klxster's known setups or 2206 jet kit then or after? I'll mix in the air box mods as needed for the jets and exhaust. I don't mind wrenching, but any recommended order or initial setup is appreciated.

9. I've seen "lidless cvk" in some of the posts. Is that a carb mod, can you point me to a thread on the details?


Thanks!

 

Welcome. You have some nice plans. Thanks for spending time reading up on the bike and mods and offering well thought out questions.
I'd do the exhaust, airbox, and jetting all at once. They are all interrelated. The 2206 kit has a more aggressive needle taper which was designed for the klx300, so we tend to think it may do better with 300 + bores and the 351 kit. If you're not going 351, get the 2152 and follow klxster. He took the time to figure this out.
I can't say Barker is better. I'm FMF now and had a noisy, raspy HMF at one time.
Don't worry about O2 tuning unless you have time and money to burn. Follow klxster's tune. If you do have time and money, it will be interesting to watch your findings and tunes.
You'll know if you want to drop counter sprocket after you put in enough time. This is not at all a one-size-fits-all decision. I like to find a rear sprocket where I can run 13, 14, & 15 tooth counter sprockets and I typically run a very large rear sprocket because of the places I ride. There's a thread here on gearing combinations.
If you find you like the klx so much you want to do the 351 kit and snappy throttle response is needed, consider a pumper carb.

 

Thanks for the quick reply. What you said on the DJ kits makes sense, I'll go with the 5152. Doing it at once makes sense, just creates a bunch of change at once, which I usually try to avoid, but where there are some proven configurations I'm sure it will be fine.

On the O2, I may do it just because I'll be riding at pretty quick elevation changes and temps and want to make sure it doesn't get too lean or rich on me and figured that will avoid some guesswork. Plus I like the tech, so if it's $150 or so I'll probably do it and will definitely share results.

 

I agree, usually one mod at a time. But here the exhaust, intake, and jetting work in conjunction and like you said, we have good tracks to follow.

The CVK is pretty resilient to elevation changes. Tune so it's not too lean at low elevations and ride. But if you're spending a lot of time at greatly varying elevations, I can see your interest. I use a Kouba screw on the pilot circuit which does provide noticeable improvement, particularly leaning out the pilot circuit at high elevations.

 

Without the MCM, and with the Barker and lidless airbox with lidless DJ144 CVK setup, you'll have power that feels pretty close to stock below 5k rpm but "comes alive" above that, all the way to redline (10,000 rpm). With that mod combo, you will have the most HP available with the stock engine/carb ( likely above 25hp ) .. So, as long as you ride in the upper 1/2 of the rpm band, you will be quite happy with the results..

MCM greatly enhances TRQ below 6k rpm and only costs a fraction of a lb ft in the power band above 6k rpm..

With full exhaust system, lidless airbox (and lidless CVK setup, of course) BUT WITHOUT MCM, the 2206 kit is the better choice. The DN053 needle controls midrange fueling better than the DN0228 (2152 kit) and has an aggresive top end taper. Also, a larger pilot jet is not as "mandatory" with your purposed mod combo as it is with other mod combos..

IMO, I concur with IDRIDR in that a 13 tooth primary should only be considered after gaining experience with the new power on the stock sprockets. Your purposed riding certainly does not imply the need for a 13 primary..

Follow the lidless CVK setup recipe to the letter with absolutely no deviations. The link to the CVK lidless setups are on my signature line - you will use the "full fmf" recipe..

Using a wide band AFR meter to make effective tuning changes requires a great deal of knowledge about AFR's, your ignition system regime, the interworkings of your CVK, etc, etc. This is hard knowledge to acquire.

 

Thank you both for the info, very helpful. I'll look through the other threads and post up once I have some good results. Riding in the upper half of the rev range shouldn't be a problem.

If I do put an afr meter on there it will be to see basic info just to look for any real fat or lean conditions that would lead to a screw adjustment or one of the other known good configurations, based on the work of others no need to reinvent the wheel.

 

Re-read your top post. In case you don't know, you have two choices for a higher performance airbox/CVK combo. Lidless or not lidless. Lidless requires one of the two lidless CVK setups (which one depends on the exhaust system a peep is running..) Any other airbox configuration will have the lid on the airbox and those permutations are "covered" by the CVK setup options within the DJ 2152 kit. The use of the 2206 kit with lids and snorkels is unverified (experimental).. Never, ever, drill your slide or "modify" your stock slide spring, regardless of which kit you are using.. The lidless+Barker performance increase will be profound - significantly increasing the bikes' capability and changing the way the bike needs to be ridden..

 

I may run the airbox full lidless, if I print my own it will be used only if I think I can get a bit more laminar flow and equal cfm with some added protection from desert dust. If it works I'll share the details, if not it will go in the recycling bin. For install checks I will run lidless and experiment from there.

You said a "DN053" needle, but I think you meant the DN0352 needle from the 2206 kit? The kit doesn't include the larger jet size, do you have a recommended vendor for individual jets?

When you say lidless cvk, is this just referring to the jetting, needle & notch, spring, and fuel screw setup in your dyno recipes, i.e. a setup to work for the lidless airbox. I thought maybe there was some other physical mod made to the carburetor I was missing outside of swapping the components.

One new thing I was thinking about. I'm guessing there's more than enough flow through the stock in tube fuel filter to keep the bowl well fed under all conditions. Has anyone found a benefit from removing and putting a bigger inline filter?

thanks!

 

In reverse order:

Stock fuel filter is proven "good"..

Lidless CVK , for you, is using the recipe for the "full FMF" (DJ144 main jet, clip on 1N with both washers glued above it, stock spring, stock lift port, etc etc ) .. While optional, if you want the very best, also get a #40 pilot from Kawasaki, and a Kouba fuel screw (for "dialing back" the pilot jet at higher altitudes)...

Yes, I meant DN0352.. I have no idea what you mean by "larger jet size" when referring to the kits as nothing in either kit is usable to you except the needle, clip, and both washers - you can throw everything else away. Order, from DJ, a DJ144 main jet and a few extra washers (in case you lose a few,,) Alternatively, you can use a K158 main jet.

Added protection from "Desert dust" does not make any logical sense. WIthin the confines of a KLX250S airbox, the volume of debris that is collected by a 25hp engine is greater than that collected by a 18hp engine - the only way you can collect less debris is by lowering your power levels with an "ever restrictive" intake tract ----- In fact, if you want ZERO desert dust, completely close off the airbox and push your bike on the trip ! Seriously, the airbox top is protected well by the surrounding structures. Open or snorkeled, the airbox draws from the same "pocket" of space under the seat, the only additional debris collection you will see is from the larger power levels you enjoy..

Now, having said that, some feel they MUST run the snorkel and don't care about the power loss.. If you are one of them, just follow the DJ directions.. but do not ever drill your slide or modify your stock slide spring !

 

Thanks for the info.

As said on the airbox, if I can't get the same cfm from my design I'll run lidless no problem, I'm not opposedto it. I've seen your posts so I know you like science, have a bit of a background myself. Really plan to just to direct the flow smoothly into the box, if possible with less dust. If you think about why velocity stacks are used on some throttle bodies it's to get more air not less, but for my original question it's moot as I said that I was looking for a lidless recommended setup which you've provided.

It will be a bit before I order and install, but will post up once complete.