I hope that this read will give a little insight to this bike and prove of some value to those looking to buy a bike like this. Let me start out by saying this bike was never meant to be for me, but for my girlfriend who was getting into dual sport riding for the first time. She is 5'4" so her stature combined with her inexperience severely limits what kind of bike she can ride.
We bought her first bike a few months back for riding out in the desert. It is a crf 230 and a great beginner bike for anyone desiring to learn to ride in the dirt and I highly recommend it. Having ridden it in the dirt I found it fun and a bike you can really develope your skills on before moving to a bigger bike.
When she expressed the desire to move to dual sport riding which better suits us as we can leave straight from out house I started doing some internet research. We went over to Chaparral to sit on the dual sport bikes in the 250 range and found that the Suzuki version was too tall and more of a full size bike. The CRF 230 was ok but I had read that the dual sport version was low on power. The KLX 250 SF had the shortest of the seat heights and it looked good overall. In the three bike shootout it was rated the best of the three so we set out to look for a used bike.

We found a 2009 with under 1200 miles on it and looked like it was well taken care of. I regret to say I never test rode it. My girlfriend hopped on it and took it for a spin and came back with a big smile on her face so I figured it must be a nice bike. So we loaded it up and took it home. We went for a ride that very day and that is where the disappointment started. The bike didn't want to hold an idle unless you started it up with the choke on for at least 5 minutes. Then once you pushed the choke in the bike didn't want to run just off idle. If you grabbed a hand full of throttle it just sputtered and coughed and slowly started building throttle. This feature never changed no matter how much you rode it. Then when she would kill the bike or stall it the silly thing was nearly impossible to restart with or without the choke. Power was severely lacking in all areas. The sweet spot of 5-7k rpm as mentioned in review articles was never so sweet. I got on the bike about 3 weeks back and was ready to throw it in the dumpster!

My friend's wife has a ktm 250 EXC so I went over and jumped on the bike and it is night and day difference. They dyno'd the bike at 38hp and it felt really nice for something that was nearly stock. I came home and looked up the specs on our 250 and was about to cry when I saw the 18 horsepower figures that people were getting. How is it that a 250 bike can vary so much between manufacturers? Well I figured I was stuck at this point and set to figuring out how to make lemonade from this lemon.

Enter Bill Blue... I stumbled across his website in looking for true performance mods. for this bike. I gave him a call and expressed my concerns over this bike and he told me they were nothing new and a chronic problem with the KLX 250. I wasn't interested in bandaids for the stock carb. and displacement and Bill assured me the 351 big bore kit and 34mm Mikuni carb was a step in the right direction. So I tore apart the motor and shipped off my cylinder and put the stock parts in a box...never to be seen again. A few days later the new cylinder came along with a block off plate and new pumper carb.

I should also say that this is the first time I have torn into a 4 stroke bike and for anyone considering this conversion I would recommend diving head first into the conversion. It was easy and very straight forward. Difficulty level on a scale of 1-5 was maybe a 3. The conversion threads on here were very helpful and downloading the manual gave me the torque specs needed.

I assembled it in my free time and overall I would say it took about 2-3 hours. After topping off the fluids I cranked it over without the choke on and it fired to life with ease! I have a 140 jet and 40 pilot. and live about 500 feet above sea level and ride mostly from there up to 6500 feet. Anyway I let the bike warm up and shut it off and gave Bill a call. He let me know the break in procedure and setting the fuel/air mixture. I started the bike up and let it warm up again and made the proper adjustments. It idled with ease with no choke on. Throttle just off idle was also smooth and never stumbled. Grabbing a hand full is immediately responsive with no hesitation. That right there gave me some satisfaction. So I hopped on the bike and took it for a spin around the area. Only being able to use half throttle for break in I could not tell the full potential of the conversion but it already had more power and response than stock.

Jump forward to today....
I took it out for the first real break in doing a 37.5 mile loop of street twisty curves through the country side. I still only took it to 7K rpm and did so slowly. I took it pretty easy on the bike but it ran smoothly with no hesitation for the full run. I got back home and let it just sit there idling and it ran smoothly. I shut it off and turned it back on and it fired to life with no problems. I shut it off and let it sit for a while and turned it back on and again it fired to life with no problems. So all the previous issues are now only a bad memory.

So my impressions of the bike....
This is the bike that kawasaki should have made and put into production. Is it a power monster or fire breathing dragon? No, not by any means. The power and throttle are predictable and smooth but still does not put a smile on my face. I wish it had more explosive power on hand for a bit of an adrenaline rush. If it was a 250 bike then I would say it is as predicted but as a 351 it is pretty anemic. My plans are to put an aftermarket exhaust on it and the rejet and tune the carb. but I don't expect much from this upgrade either. Knowing what I know now I would have never bought the bike. With the time, money, and effort into the bike I am disappointed. It still has much less fun factor than my friend's KTM 250 and I have more money into it. Somehow Kawasaki really dropped the ball on building this bike. The performance is so aweful that even when you add a 351 big bore kit and carb. swap the overall performance still is less than other properly made bikes. I am sure the head has some serious issues that keep the performance at bay. But at this point I am not really interested in spending more time and money on something that just doesn't have much potential. I am going to keep the bike for now and hope that she can get her skills up enough to move to a bigger and taller bike. I hope this helps out with anyone considering this bike. As is the bike is currently a good beginner bike but would be outgrown quickly. If anyone has any questions let me know.

 

i would definally put an exhaust on it. 09s have catalytic converters in the muffler and really chokes it up. on bills site he has dynos of a stock 351 and modded (pipe and carb), modded it made 4 more hp and tq.

 

Yeah I ordered up an HMF slip on for it. It seems like people are not gaining but really losing hp and torque swapping the header pipe so I am keeping the stock one.

 

I think you might need to study-up on the different dual sports, particularly their stengths and weaknesses before making another buy.

The only similarity between the KLX250S/SF and the KTM model you speak of is displacement...PERIOD.

The KTM is a race bike with lights and license plate holder. It requires very frequent maintenance intervals in contrast to the 'set it a forget it' KLX which requires very infrequent valve adjustments and oil changes. The KTM needs seemingly constant valve adjustments and oil/filter changes to keep from grenading the engine.

If you're the type that doesn't mind wrenching on the bike frequently, the KTM is the bike for you. I don't really regard it as a true dual sport though, because it barely has enough electrical capacity to power its own headlight.

If you're just looking for something to ride on pavement long enough to connect the trails, and don't mind a lot of wrenching, the KTM is the bike for you. If you don't want to be constantly pulling maintenance, can do without the high-strung race bike nature of the KTM, the KLX is your bike.

You can't just go out looking for a 250 and expect them all to be the same. They're all aimed at different market segments. Just sayin

 

Show me some posts where it 'seems' like that.

My bike is WAY faster, and more powerful with the FMF header, and your bike being a 351, would benefit even more.

 

Couldn't have said it better Tremor, teenycar, you just don't have a clue

 

Believe there was a post from Bill on adv rider back when the 351 was new that said he lost a fraction of a hp going from the stock 250 head pipe to the "bomb". Think he had a supertrapp on the end at that time with (only) 5 discs, probably didn't matter what head pipe was on it. 5 discs wouldn't flow any more than 5 discs.

As far as the KTM, absolutely nice bikes they are. But they aren't built for longevity or extended road miles like the KLX. I have a crf20x that makes a ton more power and is lighter and quicker, but would never think about riding it cross state loaded with gear, just not made for that.

 

I agree Trem', although I think he has it even more mixed up. 38 HP from the dyno, so he 's gotta be talking 2 stroke KTM. Chalk and cheese. Why wont my Hilux corner like my buddies Porsche. Duh!

 

That's odd because I own a KTM 525 and other than oil/filter changes I have not needed to do anything to it, nor have my 4 other friends who ride KTM's. Other than upgrading the headlight bulb I find the electrical system to be equal to that of the KLX. I'm also curious what you mean by high-strung race bike nature? As in it isn't comfortable to ride? Does it have more vibration than the KLX...yes, but after my little 40 mile ride I find my KTM to be much more comfortable to sit on for the distance traveled.
I don't expect all 250 bikes to be the same but I am just surprised at how different they are for the same displacement! I tested at WR 250 this morning and it had more explosive power than the KLX does with the 351 kit at this point. Surely you can agree that from the factory Kawasaki missed the boat on this bike. Taking into consideration the KLX is a 351 displacement it still feels less powerful than a stock 250 bike from Yamaha.

 

Bill's site is a good example and there are other dyno numbers out there that show a loss in hp and torque on the bottom end with replacing the stock header pipe. You might get more on the top end but I am concerned with bottom end numbers since the bike is used in the dirt and twisty corners of street riding. Why care about top end hp on a 250 bike? It isn't like you are going to go that much faster and relatively speaking the bike will always be slow for top speed anyway.