Found some good discussion of Megabomb installation (FMF brand) on supermotojunkie today:

Un-corking the KLX250SF

Pics below in case of link rot:

 

What most people fail to consider is that the OE muffler is a structural member of the tail section. Looking at the top pic you can see the OE muffler has three mounting points. This triangulates the right side. If you plan on carrying loads on the tail section stay OE.

 

Or bolt a gusset on

 

There was a thread on making a gusset but I couldn't find it. Not sure if one could be bought.

 

Found a little time to install the 2006 edition FMF Q4 (p/n ) on my 2007 KLX250s tonight. The short story is it fits perfectly.

Here is the full album: Imgur: The most awesome images on the Internet

Some select pics below:

Q4 042156 fit snugly in the stock header (no reducer needed)



Here's the Q4 mounted up:



Top view (no turn signal melting problem here)



FMF included a spacer for the rear mount:

 

Also picked up the 1 1/8" quiet core. I live in a suburban area and don't want to **** off the neighbors (and want to keep my urban riding areas accessible).

I used a hose pick to help slide the provided core out of the muffler body (it was a snug fit).



Had to use channel locks and a towel to finish removing the larger core:



Regular and quiet (1 1/8") cores, side by side:




Significant difference in output size:



Installation is reverse of removal:



I recommend a ratchet wrench for installation of the locking bolt:



Even though the 1 1/8" quiet core is noticeable smaller than the standard core, it is still much larger than the OEM muffler:

 

Ahh, couldn't help but notice the black and red fingernail polish.. Soooo,, Queen, are you a girl..?



Colorblind..?

 

purple and red and yes am a woman

 

Cool! You don't see many women on motorcycle forums.

 

SaWeet !!!


Now, install a DJ 2152 or 2206 kit, but use a DJ140 main jet, set the clip on the 2nd notch down from the top of the needle, pull the airbox lid, fire it up and HANG ON !!