I bought an 09 KLX250SF earlier this year with a decent amount of work done to it by the PO(s). Currently the only known 'performance' mods I've got are a FMF powerbomb header, Q4 slip-on, and ground fix for the rectifier. I'm not sure how to go about finding out if the carb was re-jetted without pulling it all the way apart so that'll forever be a mystery for me I suppose. I've thought about doing the big bore upgrade and changing the front sprocket to get a bit more power highway power. I know she'll never cruise easily at 75 mph, but currently she'll hardly do 70 without the throttle pegged and me in a full tuck.

Mostly I just wanted to ask, with an FMF exhaust set, what mods would give me a bit more highway-ability for the the bike? Also, I get a lot of burble and popping when I downshift and decel. Is that normal for the aftermarket exhaust?

 

I use my SF mainly for commuting, and did mods to better suit that role. But admittedly the KLX250 will never really be a great highway bike. That being said, the mods I've done that seem to help the most include:

• More Comfortable Seat (various options)
• Taller Bars/Bar Risers
• Handguards and grip heaters for cold weather (if applicable)
• 15T Front Sprocket (Or even a 16T if you think it will fit)
• MCM (Allows the engine to make better power in the more typical cruising RPM)
• Larger Fuel Tank (At least a 50% improvement in range)

And a windshield would probably help in some situations.

I routinely ride around 60 MPH which the KLX250 can do with ease. However I occasionally hit the Interstate for short sections, and that's where the KLX can struggle a bit. Into any type of headwind or uphill, mine won't even maintain 75MPH. I think the 50/50 tires I'm running are a big part of that, so keep the stock SF style (street) tires if you're interested in higher speed stuff.

As far as the popping on decel, try removing the air injection system on the exhaust if the bike still has it. I think that can be a big contributor to backfire/popping issues. The other is jetting, which you'd have to check manually.

 

Thanks for the tips!

I'll have to check on the exhaust. I haven't messed with it much and don't have much experience with bikes or exhausts on cars.

I have a few of the mods on your list, but my biggest concern was with lack of power on the highway. I live in a small town and the only way to any of the bigger cities is on 65 mph speed limit highways where cars tailgate before blowing past. I'm still getting used to the wind blowing me around.

I guess I'm just trying to get a few ideas and see if I'd rather sinj a little money and time in the bike or buy another bigger bike for commutes. I love how easily I can bump around town and mess about so I'm worried I'd lose that going to a bigger touring style bike. Plus I'm 6'0 and 125 pounds. Bigger bikes get a bit harder to manage wrangling around at my size and noob skill level.

 

The big bore kit seems like it might fit your needs, many KLX owners swear by them and say it transforms it into another bike. You get to keep the same lightweight, flickable nature of the KLX but with a considerable bump in power. Geared right, it should have no trouble maintaining highway speeds.

That being said, if your riding will ultimately be mostly highway, there might be better options than the KLX. Even a Ninja 250/300 would be much better at those speeds, and can be picked up for quite cheap.

 

Most open aftermarket exhausts will pop a bit on decel if throttle is totally closed. If the throttle is lightly cracked it usually will stop.

I would venture to say if your idle mix screw plug has been pulled out it likely has had some jetting play. Definitely if the bike fires up easily and is off choke relatively quickly.

 

You know, I didn't think about looking for that plug. Thanks for the hint! It does usually fire up and go pretty quickly when I remember to put the battery tender on. These cold days are not it's favorite.

 

I was going to say all of those carbed models after at least 2009, maybe earlier, had to crank and crank and crank for 10-15 seconds to fire up they were so lean at idle. Doing the pilot cures it pretty fast. When the bike is run regular it will fire up cold in maybe two turns of the engine and normal spring-fall weather will be off choke in maybe a minute at the most.

 

Fishstik, you can certainly mod your bike for waay better highway performance - but it means getting into your engine (MCM - Marcelino Cam Mod) , and your carb (DynoJet jet kit) .... Otherwise, you can order Bill Blues 351 kit and his TM carb and have a shop install it all..

 

Yeah, I'm looking currently at learning all about jetting. I've been in a few airplane carbs but that's been years ago and I don't remember changing jets for performance. I'm thinking this spring I might just order the 351 kit and tear into it. I think my bike has been jetted due to the previously mentioned plugged being MIA. I plan to wait for warmer temps and give a crack at starting with just checking the idle mixture setting and ditching the smog gear.

Sadly though, I am leaning towards thinking about a bigger bike for highway commutes and keeping the little KLX for the truck bed if I go out of town. I've been checking out the CB500X, Versus 650, and V-Strom but that's another topic for a different section. Still love the KLX though... she did, and will continue to, teach me a lot about riding.

 

Nothing wrong with that. Both my brother and I use the 250s as around town play bikes and put them in the truck to go to any sort of dual sport events. If it's geared for road it sucks off road and vice versa. Both of us are geared a bit lower and tires to do the dual sporting. With a lowered Ranger flair side, I can load and unload mine alone, no problems.

My brother has a CB500X for his road play, having had a Buell Ulysses. He loved the Ulysses engine and general bike, but it was seriously tall so he went to the CB. I have my KLX650 for my road work, on which I've done a lot. It was too big for any fun off roading. My brother bought the KLX from a guy who lived 120 miles from him, but only about 10 miles from me, so I checked it out and rode it for my brother before buying. That ride sold me, I found one too. Now the 650 is going road only, soon with 17s.


If it was me and buying new if the money was there I'd take a serious look at the new Versys with the matching bags, the bags only add $600 over the standard bike. The Versys has gotten rave reviews everywhere and the couple of riders I've known of that got them loved them. A bit more street/sport than dual sport, but hey - that's what the 250 does well.

Never hurts to specialize if you have the space and money.