So I am in the process of modding my KLX250.

Current mods include: Twinair filter and KDX200 Snorkel. Its currently at the mechanics after a failed theft attempt where its getting done the Marcelino mod (This is taking them forever). Im planning on keeping this bike for awhile so in the future I might go for a Powercommander and a Bigbore kit.

Im considering ordering a FMF Q4 pipe and a FMF Powerbomb header from the United States, the fact that its the quietest of the exhaust system and the looks and weight of it appeal to me. However, it comes with a hefty price tag due to all the import taxes.

My question is then: Can you actually feel any difference with the header on the bike? Has anyone compared performance of the KLX with a slip-on only vs. the full system?

Any general feedback about the Powerbomb header will be appreciated too

 

I noticed a little power increase after installing the slip-on. It's definitely a lot lighter then the stock muffler.

As for the header, there are varying opinions if the cost is worth the power increase (if any). I still have the stock header. If I found a used one cheap I'd probably buy it, but it's pretty low on my priority list.

 

I have the Powercore on my bike. I've noticed a power increase, but the feel is biased by the EJK controller that went on the bike along with the pipe. Which brings us down to the fact that you should get a controller if you plan to use a free flow can like the Q4. Don't expect the stock ECU to make corrections for the increased flow. Specially that you already have a KDX snorkel and better flow air filter. You'll run dangerously lean.
I would even dare to say to drop the header and get the controller instead. You'll have much better bang for your buck and keep your engine happy for the long run you intend to do with this bike. Mine rode over 52,000Km in the past 2,5 years and it still is a healthy girl. I've also done the cam mod (20,000Km ago) and I like it with nice torque and power increase.

 

As you have an EFI bike, if you are considering a big bore kit in the future, you will need a fuel controller. Either Powercommander or EJK. I used 2 different types of EJK.
One for standard 250, and when I did the 300 and finally 331 big bore, I used the reprogrammed EJK.
Now in my opinion, I started out with the pathetic wheezy little 250 EFI and started throwing money at it. Lots of it, looking for power. Leo Vince Tailpipe, nice sound, power increase? who knows? FMF mega Bomb, more sound changes. Power increase? Maybe I could feel a little because I spent so much money I wanted to beleive there was more.
EJK and Uni filter was next. I must admit that pulled the package together by flowing more fuel and air. Was the wheezy KLX suddenly a fire breathing wheelie monster? Nope.
I then popped in a 300 Jug and the whole scenario changed. Suddenly the KLX started to feel like this is what it had been designed as in the first place. Whole different bike. Exciting.
So then I went the whole nine yards and threw on a 331 kit with 101 Webcams and I am finally stoked. Still not a fire breathing monster, but behaves calmly at low revs with plenty grunt, and roars all the way up to 10 K, pulling like a train. ( maybe a small train)
So to cut a long story short, put all your money towards a 331 Kit and a fuel controller.
Keep the standard header and change just the but plug in your standard tailpipe, and I promise you will have a great performer. Later when you want to spend again, go for the noisy bits.
Bang for buck, Big Bore.

 

Thanks for your feedback.

I realized that the FMF Full exhaust system costs as much as the BB331 kit, so its a bit silly to spend so much on the exhaust system for minimal performance gains....even if it does sound cool.

For economic reasons, I cant really spend more than 550€ every 3-4 months on this bike. This means that I have to plan my upgrades in stages. Some upgrades require other parts to be upgraded as well. (i.e. you cant do a big bore on an EFI without getting a Powercommander) It seems then, that my best bet is to start out with buying a Powercommander V and then stick with the stock exhaust but change the buttplug to a bigger diameter.

Is there any previous threads on how to change the exhaust buttplug. Is it straight forward? Do I need to weld aluminium or anything like that?

As I understand it I need a Powercommand map that matches my setup. If that doesnt exist, I need to make my own. I know there is a local guy doing professional powercommander maps who has a very good reputation for perfection. The only problem is that he charges as much for his service as the Powercommander costs in the first place...however it might be the only option.

Any idea where I could get a map without paying a guy big bucks to make it?

Then in the future I would have everything in place for a BB331 kit. I must say that I am worried about customs with this BB331 kit, especially considering the "core charge" and having to send my piston back, it sounds like this process could easily be made very expensive by complicated custom laws.

 

go mega bomb it is quieter and more power then power bomb

 

If you look somewhere Marcellino posted a picture of his but plug conversion. You will need to search a bit under his postings.
The stock EFI mapping can handle these slight changes quite happily.
I use the EJK controller made by Dobeck performance. Check out their web site. Very easy to tune it yourself. No computer required. Comes pre tuned for the 300/331. Costs around 150 to 200 bucks. Only issue is that there are 2 different models of EJK, one for 250 and another for 300 plus. So decide if you are going big bore and order the one for 300+.
There is such a slight power gain by doing all the pipe/powercommander/whatever on a 250 that it is not worth it in my experience. Get a EJK get a 331 and you are laughing.
I am extremely happy with the EJK and can tune it while I am driving if I want to lean or richen it up. Just press buttons as it mounts on your handle bar mount right in front of you.

 

Very interesting information. I had actually not looked into the EJK controller at all because I didnt see a lot of talk about it. Everyone was talking about the Powercommander. After import taxes (EJK is American product) it will end up costing about the same as the powercommander. However, the EJK controller can be controlled by myself. With the Powercommander, I would have to pay a guy 300€ to make a tailored map for my bike everytime I made changes which is what I dont like about it. EJK I could control myself, for free! That being said, with the Powercommander you can get a map that is PERFECT for your bike, which is pretty cool.

So while the PC V will allow me to get a perfect map for my bike it comes with a hefty price....the EJK makes the most sense from an economical perspective. This is a pretty strong selling point considering that this is an "economic" bike in the first place.

How easy was it to set up the EJK with a good map? Do you get flat spots, surges or anything like that or did you manage to set it up so it runs good through all the RPMs? You said you can change the mixture while driving, why would you need to do this if you had already set it up to be ideal?

 

The EJK makes use of the standard map on your bikes ECU. All it does is introduce more fuel at 3 different throttle points, namely cruising, acceleration and full throttle. So the first 3 buttons control this. Next 3 buttons control switch points, which means you can adjust the point where cruise, acceleration and full throttle meet each other. So simple.
I live on an island that goes from sea level to 1000 meters straight up. There is no standard map that will accomadate these two extremes perfectly. If you had a carbed bike you would need to change jets for 1000 m when playing in the mountains, and then rejet for sea level, or just live with the slight burbles, splutters and backfarts common to 4 strokes.
I set my EJK very simply after going from 300 to 331 with added Webcams. I looked at the DOBEK website, recorded their recomended settings for a 300, pressed some buttons and was 90% perfect. The only thing I changed was going slightly richer on 2 of the buttons to allow for the extra 31cc and cams.The jetting is now as close to spot on for all altitudes and all weather conditions. No flat spots, no burbles, no surges.
Now back to your question, why change on the fly? If you are going for a long leisurly cruise around at sea level along miles of freeway, and you do not intend screwing the cr@p out of it, press button number 1 to lean it down and save some fuel. Feeling frisky? Dial in a bit more gas and wind it up. Simple.

 

I love this website, its a goldmine of information!

So that means you dont need to eliminate the 02 sensor either? Interesting...

After what you say, I think I will have to go with the EJK controller over the powercommander. It just doesnt seem like its worth it with the Powercommander when trying to save money. I would need to pay someone to do a new map everytime I added another upgrade. Its too much... EJK seems much simple to use. Did you buy it straight off their website? Ive done google search but its the only place I found it for sale. Costs 225$ there.

Now, if only I could find a way to buy the BB 331 kit. Im worried that customs will screw me over with the core charges of the cylinder. I dont want to pay import tax of that bit when its something that will be returned.