I found a KLX 300 muffler for $30 and the header for $35 on e-bay. Took a while to get both though. Then bought a CNC'd tip and backfire screen for another $35.
Improved the sound, without being obnoxious. And no fitment issues, or melted turn signals or airbox.
Bike sounds as it should now, IMO.

 

Your quietest aftermarket option is the FMF Q4 but it isn't quiet. It's nice.

With regards to sound tests at woods races... I get tested all the time before nearly every race and it is rather disappointing how different the results are each time. We're talking huge swings depending on the tester, ambient noise, testing equipment, etc.

I would look for the KLX300 pipe if you are concerned with quietness.

 

+1
exactly the same thing here. I think the biggest variable is the operator of the test equipment.

 

I almost jumped on a DG, because they're cheap, and a friend recommended them... then I saw how loud they are!!! They could quite likely be the loudest aftermarket available for the KLX250. I ended up spending a little more and went with DEP. Couldn't be happier. People tell me my bike sounds exactly like a 450R now.

 

The TB exhaust is loudest, but the DG is loud I guess, for me its great, my truck with a 454 and glasspacks is louder. So the DG is quiet to me

 

DEP exhaust? Never heard of them, nor has Google unless that stands for something and I'm blanking out?

As for the Two Brothers - I have those on both of my streetbikes and yep, they are NOT quiet! One of my local roadcourses (Arizona Motorsports Park) has a noise restriction of 94 db and I was able to pass after re-packing and putting in a silencer endcap. I probably wouldn't care about the noise on my KLX, except that I'll probably get a wild hair up my bum and throw some slicks on it for a track day...

Then again, I'm just about to put the 351 kit in with some Web Cams, maybe I'll just go ultra sleeper mode and leave the stock pipe on!

 

Yeah - it's DEP. More popular overseas... just making a name in the States.

www.deppipesusa.com/

Here's the link to mine (KLX250):
DEP Pipes

If you want a wicked-sounding pipe, not something that's "just plain loud" you should look into DEP. Never heard anything sound so good on a 250cc 4-stroke, period! Just be aware that you WILL have to mod it to fit the stock KLX250 header - unless you have a KLX300 header which has a larger diameter outpipe.

 

2012 klx250s
Just over the weekend i had my bike inspected (total stock) 76db @ 4000 Rpms no load 20 inches away from the pipe.
this coming week i'll be installing the FmF Q4 with the denise kirt quiet insert I'll report back and let you know the findings

 

Can you test it with and without the quiet insert? Thanks.

 

I'm really interested about your test, will be following. By the way, what is the "Denise Kirt quiet insert" can't find any info on Google?