No, its not the same 250-- the engine in the Mojave and the KLR 250 is basically the older brother of the KLX 250/300 engine. It has a very similar (not exactly identical, obviously) bore and stroke, DOHC, 4 valves, and liquid cooling. One difference is that it uses rocker arms between the cams and the valves, while the KLX engine is a rockerless design.

The Mojave/KLR 250 was/is an awesome engine, but one of the few gripes about it was the fact it used rocker arms to actuate the valves. The KLX engine is essentially a KLR 2.0, eliminating the rocker arms.

Visually, the engine designs are extremely similar, from the oil filter type and location to the KACR compression release to the PITA spark plug placement and access. They also both use CVK34 carbs. I consider myself to be a bit of a Mojave afficionado, owning two of them and having done quite a bit of work on each one. They are awesome little quads, Ive spanked 300exs and Blasters with them.

The Mojave/KLR engines have good low end, incredible midrange and very good top end power-- to be honest I was expecting similar power characteristics from the KLX but was pretty disappointed when I first hopped on it. It felt very anemic vs. the Mojave, even stock vs stock. Really poor low end power, OK midrange, and tended to want to spin the wheel in the gravel once the RPMs hit about 6500-7000 or so, yet the top end still felt a bit lacking. To be sure, part of the top end problem was the super plugged intake and exhaust setup, but the low and mids could definitely be the valve timing.

In theory, the KLX engine is similar enough in bore and stroke that similar valve timings should yield similar power characteristics to the Mojave. What the MCM is doing is essentially tuning your bike like a quad.

The reduction in airbox noise also makes sense-- if the intake valve opens later (stock KLX) there is more vacuum developed in the combustion chamber, thus more forcefully sucking in air in a shorter period of time than if the valve opened earlier with less vacuum in the combustion chamber at the time of opening.

One thing I do not know is if the valve timing of the KLR 250 differs from the Mojave-- it would be very interesting to see. Ill post if I can find it.

 

You anemic performance will soon be ancient history. Do-up MCM, DG-O, choose a setup for the CVK(near sea level): DJ2152 kit with a special ordered DJ140 main jet, set the clip on the second notch down- 2N - on the kits' DNO228 needle, put in the DJ140 and the DJ slide spring... OR, set your N1TC on 2N with a K152 main jet and a drilled slide on the stock spring....

Pull the airbox lid off..

You're done.. And you'll never look back.. SAE corrected numbers of right at 22hp/16trq of rear wheel power..

 

How important do you think drilling the slide is? Ive heard arguments on both sides, but one thing they both agree is that it doesnt add any HP, just changes throttle response a bit. Does drilling the slide actually pull the needle up quicker or make it require more vaccuum to pull up thus making it slower? Ive read both.

I have the N1TC needle, but I took it out after my first go round where the K135 MJ and the needle at 4 notches down had it WAY too rich-- but that was before the exhaust upgrade and I still had the backfire screen in place.

 

It may be the difference in lofting the front wheel for a rut or log, or maybe getting enough run to make it up a hill. Fact is that tenth might be better for me than any boost in peak horsepower. Also the reason I did the MCM, to get increased torque.

It definitely is good to gain any quicker response possible when working with around 20hp for sure

As I said, my next move is to eliminate the lag of the CV carb entirely with a direct cable operated flat slide.

 

Hey Josh, let me see if I can help - the drilled lift hole+stock spring or standard lift hole + DJ spring controls the fueling offered by the needle during all needle fueled operations - The needle is nothing more than a variable valve for the air+fuel that is created in the needle jet. The needle jets' A/F characteristics are controlled by the main air jet and the main fuel jet.

The lift hole, spring, needle, and main jet (not main air jet as our MAJ is not replaceable/tunable) must be built/configured to work in unison to provide a useable fuel curve. Therefore, it is a "recipe" of carefully chosen components that can create maximum power levels.

Drilling the hole allows the slide to react to vacuum changes more aggressively. The Dj spring offers less resistance to the slides' movement and the stock spring offers more resistance - therefore modulating the effect of the slide lift hole regardless of it's size.

My KLX300R is using the DJ2206 kit with DJ146/3N - this kit calls for drilling the slide and using the stock spring. So I get to compare a drilled slide to a stock slide with DJ spring - It is my belief that either offers about the same slide functioning.

Lets do-up a senario: DJ 2152 kitted, DJ140/2N, lidless, slipon, near sea level - Put the stock slide spring back in and the entire fuel curve slides to the right on the RPM scale. This will cause the bike to run leaner during all needle controlled fueling operations. At WOT, it will run leaner below about 7k. It will also cause the fueling to be less responsive to throttle input which also equates to leaner responses to throttle input. All of the above means less HP and TRQ while operating within needle controlled fueling and less throttle response everywhere.

Changing the clip position will change the fueling offered by the needle - The lower down, the more rich the AFR could be during all needle controlled fueling. It is a tap dance between the hole/spring/needle and needle clip position as to how quickly and how much the main jet is "uncovered".

As it turns out, the dyno shows that a proper AFR, therefore fueling curve is created from 4k to redline, for max power and throttle response, near sea level, with a lidless airbox and a slipon, using DJ140/2N and the DJ slide spring. From creditable member reports, using an apparently well designed jet crossover table, an alternative is N1TC on 2N with a K152 main jet and a 7/64 drilled lift hole with stock spring.

The N1TC has a taper that is extremely similar to the stock NNLA needle. - it is, however, quite a bit shorter and carries larger diameters over its' length compared to the DNO228. You need to know that lenghtwise N1TC @ 1n = DNO228 at 4N - The takeaway is that N1TC is only useable on 1N and 2N due to its' shortness, in a recipe that sizes the main jet correctly for max power. Also, the only reason 2N can work in certain situations is due to the larger(leaner) diameters of the N1TC over the 228..

I hope I have given you the help you were wanting.

 

Josh, here are the needle measurement threads from me and PWJM.

https://www.kawasakiforums.com/forum...urments-43117/

https://www.kawasakiforums.com/forum...-teaser-43153/

Hey before you go to those threads, the instructions on this webpage (http://planetklx.org/techtips/dynojet.html) are talking about the DJ2206 kit. It is an old kit designed for the KLX300R. It will work just fine in our KLX250's. The components are quite different though.
It calls for drilling the slide with an included bit, and its' DNO352 needle is quit different from any of our "250" needles. This kit is/was designed to work with the lid off. You can see a pic of this needle in one of the threads above..

 

Thanks.

 

Thanks for the info, very informative. If it was me and you wanted the "feel" of the Mojave go BB 351 and TM36-68. No comparison and it will give a nice arm stretch that the 250 never will.

 

Sounds good-- my only concern is that some say drilling the bleed hole can cause some erratic behavior at very low RPMs- ie rock crawling, tough terrain, etc. That and once its done, theres no going back. Did you experience any of this or any other notable negatives from doing it?

On a side note, I worked on the carb yesterday for the first time since installing the DG O-Series. Put the N1TC, used 2N, changed to a Keihin #138 main, installed the Kouba fuel screw. To be honest, I thought it was probably going to be a little rich, as I still havent cut the BF screen yet, but it pulled much harder in the mids to the top. In fact, I may even try 3N on the N1TC to see how it reacts to a little richer mix.

So I went from:

Bone stock: #118 Main, #135 pilot - super cold starting, long warmup time, zero bottom end.

Light Mods: #126 DJ Main, #140 pilot, Uni filter, Drilled holes in airbox lid, stock needle with 1 shim, drilled spark arrestor/baffle in stock exhaust - Much better starting and low end response, noticable increase in mids, similar top.

Current: #138 Keihin Main, #140 pilot, Uni, N1TC @2N, DG O Series, Removed airbox lid (cant hear the airbox noise anymore with the DG). - Much harder hitting and pulling mids and tops, low end seemed to benefit a little as well.

I plan on installing the 6dB DG baffle very soon (on order), so I really dont think I need to go up anymore on the main, maybe not on the needle either. That DG has some major bark to it. I may drill the slide and once Im satisfied with everything, I may do the MCM when I need to check the valve adjustment. Those MCM curves look very nice, I just really wish we could compare to a similarly piped and jetted non-MCM bike.

Another question on the N1TC-- on the KLX300, there are two different needle jets available, neither of which matches the stock needle jet on the 250s. KLXster, are all your runs based on the stock needle jet?

 

Anyone using a KLX250 for low rpm rock crawling has rocks in their head...

Just sounded kinda funny...

Trying to crawl around on any 250 at low rpm is an invitation for a headache. They don't build any good power until 4000 rpm. It is nature of the beast. Someone wants good low end buy a trials bike. To get that kind of performance from the KLX with any good results would take a retune losing hp, but gaining low end. Probably a 32mm carb to get good low rpm carburetion. The two strokes use tiny ones, the old Bultaco 350 T ran a 24mm versus the 26 run on the 250s, but that thing was a tractor.

Just sayin' trying to make the bikes do something outside their envelope of performance will usually have bad results. Trying to lug almost any 4 stroke single dualsport or enduro below 3000 rpm under a serious load will usually result in the engine bucking, they just aren't made to run that way. My 650 does not like reving under 3000 rpm pulling hard. It is best from 3500-5500. The 250 doesn't really feel good until 4000 and better yet at 5000.