Welcome to the forums. The diference between the stock 300 exhaust and the 250 exhaust is the diameter. but when you go and buy an aftermarket exhaust suck like a muzzy the header size increases.

Hey jrock the best choice in my book would be the muzzy. i have heard and seen about the big gun: bolts can strip out and the can does not hold up as well from what i have heard.

 

I, too, have heard some questionable things about Big Gun. Personally, I'm saving up for a full Muzzy, probably several months down the road, but that seems like the best bet in my book.

You'll get alot of guys here telling you to go with the kit for the KLX300 but I'm of the mindset that the kid made for the '09 250S is the way to go simply because it was made specifically for the bike. Both are good kits and give great results, but I would rather have something made for my bike, not just a kit that's been around. Totally IMHO though.

Welcome to KF, markcr!

 

Thanks for the info and welcoming me to the group. I've ordered the DJ 09 kit and will follow the instructions for the stage 2 setup. The full Muzzy seems to be the way to go but like most of us, it will have to wait until I replenish my cash pot! I have to say, I was pretty impressed when I test rode the stock 09 at the dealership. I went in with low expectations and came away with a grin on my face. I recently test rode a new KLR650 and from a horsepower to weight ratio, I didn't think the KLR was THAT much more powerful. Different bikes completely but it just goes to show that the little KLX has some grunt. I currently ride a BMW F650GS Dakar which has power to take you to the moon. It's a blast on the highway, twisties and fire roads but on the trails is not where it shines. Lay it down and you're in a world of hurt (financially and physically). The thing weighs about 450 lbs! Plus, for the price of a BMW replacement plastic I can buy an 09 KLX250S. Anyway, I'm thinking about breaking in the new bike completely stock then taking it to get it dynoed in "off the showroom floor" configuration. Then I'll do the mods and dyno it again. It would be really cool to have and share that data with the forum.

 

nice discussion newbs, but just remember that the stock 300 header and the stock 250S header are the exact same pipe sans about an inch of length for the 300 header as it's longer. But the diameters are exactly the same. Slip-ons for the 300 will not fit the 250 unless you install the 300 header. There are some exclusive 250S slip-ons made for that bike; 2-bros, HMF, FMF.
Also, there is nothing wrong with the BG. I had a full BG EvoX system on my '06 KLX250S and it was a work of art and fit better than the stock system. It sounds tough and makes gaudy amounts of power. If I hadn't of found my full Muzzy for $100, I'd have another BG on my '09. The new BG systems are all stainless as well.
As far as jet kits go, the new for '09 kit is okay, but the 300 kit gets you the better tapered needle which is the key to power delivery.

 

Yeah, there seems to be a lot of discussion on the differences between the 09 250 jet kit and the 300 kit. Naturally, I ordered the 09 250 kit before I read your post. Doh! I sent an e-mail to Dynojet with some questions about the 300 needle and slide drilling vs. the 250 needle with different spring length. It will be interesting to hear what they have to say. I'll share the reply with the forum when I hear back. I wonder why they don't suggest to drill the slide lift hole in the 09 250 kit? I can't see where a different spring length would have a similar effect.

 

I bought the 300 kit...

My thoughts...Either or and you will be happy..300vs250..The difference is the mechanics dialling in afterwards and the air cleaner..And sprocket count..

6 in one hand and a half dozen in the other.....What you get is a funner bike and worse gas mileage.....But worth it....

My call is a 13t is needed with this mod...Our stock gearing you have to work for in gear after 1st gear.....A 13t gives you that matched gearing with less throttle......Im even betting top speed is higher because I dont need the extra mile to go faster...

Rocco..

 

I believe I remember the spring in the 250 kit is different than the stock spring length-wise, but don't quote me.

Changing the sprockets is a personal preference, IDK if I'd call it neccessary. I won't change my sprocket because I ride too much road. If I rode more trails I'd consider changing the rear sprocket, but gearing it down kills the dual-sport end of the bike. I doubt you'll get any higher top speed because your gears will be shorter; you'll run out of engine speed... unless of course you're talking in the woods, cause yeah, you'd probably be able to actually top out.

 

as stated, the spring in the '09 kit is of a different rigidity assumingly, making the drilling of the slide unnecessary. the spring has the same effect on the butterfly by not being as stiff. the drilling of the hole has the same effect.
as far as the '09 and a 13-tooth front sprocket, well, also as stated it does kill the streetability of the bike. On my '06 KLX250S, I did the 13-toother and it really helped the bike. But the '09 is different; I installed the 13-tooth on the '09 after the Muzzy and other listed mods and really all it did was raise my rpms and limit the streetability of the bike. First gear is downright useless and in no time, you're turning 7000 rpms at 60mph. That's not any fun for any extended amount of time. The '09 tranny was reworked and sixth gear was recut and brought closer to 5th gear. It will pull top gear no problem especially with an exhaust upgrade. So unless you're truly using the bike for trails 95% of the time, I would actually discourage a 13-tooth sprocket on the '09. I've got mine sitting on my bench with under 100 miles on it. I put the stock 14 back on and love it. I've said this from the gitgo with the '09, even in stock trim I didn't think it needed it but I wanted to try it out. For off-road use though, I'd use it. But for my style of riding, doing 65mph at under 7000rpms is what I'm wanting to see.

 

Just letting the newbs, as you put it, know whom they are taking advise from...Muffler King.

Call dyno about the needle difference between the 09 and 06/07 kits, if any. I'm betting there is no difference besides jet sizes provided, the spring and drill bit.

Unless you plan on going up in cc's to a 300 or 331/340 the full muzzy may not be the best choice and a cheaper slip on may be better to keep a little low end grunt.

BTW I have had the muzzy on my klx with a 250, then 300 and now a 340....works real good now and low end is not a concern now....also it is a tough pipe...lots of salt water and get off's.....still looks sharp, but real loud for a 340....oh and over 8k miles beating the snot out of her.

Carry on Muffler King

 

Well after almost 40 miles of trails, an exhaust moved down my list of KLX needs below TIRES! Power wasn't a problem, I kept spinning and washing out with these drag radials. I do see that gearing is a good option for the tight stuff; I had to do a lot of clutch slipping in the tight and technical, I just ride too much streets for gearing to be something I would pursue. However, it definately would help.

MPG UPDATE: 52 miles, of which ~35 were trails, I got ~47 miles to the gallon.