You do have options, since you are willing to spend the money. Food for thought.

• Have a turn down tip welded on the end of the exhaust. My brother did that with a flange and pipe bend on his KLX300 muffler.
• You might be able to have the KLX300 muffler mid pipe expanded in diameter by a muffler shop, to fit the head pipe, seen that before.
• You could have the mid pipe cut and a piece of pipe welded in to fit the header pipe, again, maybe a muffler shop can help.
• You could find a used sport bike can (longer) and do the necessary mid pipe work to fit it. You can shorten it up too if too long. A friend did that with an old CBR600 can, making it fit his XL600R supermoto. I don't remember how loud it was though. Muffler shop again.
• You could do the "John Deere" modification done by some KLR riders shown in the KLR.net forum. Need I say... muffler shop, but also a farm supply store for the muffler.

It's a shame no manufacturer can make a chambered high flow muffler. Flowmaster and Magnaflow do it for cars. It would be nice if they did a universal can for bikes.

 

If that JD muffler is straight through it would be just as loud as a PC4 from FMF. Attempting to go the opposite direction.

Interesting idea about the road bike slip ons. I could envision that being time consuming ordering cans, modifying each to fit just to see how loud it is.

Agreed about lack of quiet options for aftermarket pipes. Cheaper to build these straight through designs then market them with cool names to make the noise seem desirable.

 

I'll check on fitment of the KLX300R stock muffler with my Megabomb either tonight or tomorrow at the latest.

 

Never could get anyone there to post a video with sound. Go to a farm store and look down in one. Find a chambered muffler, doesn't have to be JD.

Problem with the sport bike cans - straight thru.

I'm going to the Goodguys car show next weekend, I'll have to look at the muffler guys to see what's going on.

Here's a video link for some stuff on mufflers


I've thought of trying to do the turbo style muffler internals on a reverse cone megaphone. But that's as far as I got, need to finish the SR to do the work.

 

Here are comparison photos of the OEM KLX250-S muffler next to an OEM KLX300R muffler. (apologies for first pic blurriness, I need a better camera app).

Muffler inlet stinger
KLX250S: 1 1/4".
KLX300R: 1 1/2".

The KLX250S muffler appears to be 1 (one) inch shorter than the KLX300R muffler.

Both mufflers are spark arrested. Both have "LX250S" stamped on the manufacturers plate, though the KLX300R has a listed DBA of 82. The KLX250S has a listed DBA of 80.

Going riding today in mountains where I can be a little louder so the FMF stays on the bike for now. Will test fitment next week as I am able.





KLX250S:


KLX300R:

 

Here is the OEM KLX300R exhaust on a KLX250-S with FMF Megabomb. It does not fit properly when everything is bolted up.












The FMF Q4 slides way up in the Megabomb header, past the cut slots you see in the pic below. OEM KLX300R muffler only goes in the Megabomb header about 3/4".

 

Also got my used KLX300R header in today. It's 1 1/4" in diameter, then steps up at the stinger to meet the larger KLX300R inlet.

So for now I'll plan on swapping entire exhaust system when I want to ride stealth.

 

Ok, so there is a header/midpipe length difference.. Thank goodness as that is what the forum has always told peeps.. You need a pipe stretcher..

It looks like your 300 can has an aftermarket or homemade tip.

Is it quiet enough for you?

 

No pipe stretcher - the KLX300R does not fit far enough into the Megabomb. There is only 3/4" of contact and that is being generous.. maybe only 1/2". See pic above. Even if the Megabomb were longer, using a pipe stretcher on it would mean I can't use the Q4 anymore since it will no longer seal properly.

I have a working solution now, so I am not going to damage my $$$ Megabomb by stretching.

The OEM muffler (and I guess OEM header per photos above) are plenty quiet enough for stealthy riding. I'll keep the FMF & Megabomb for times where noise is less of an issue.

 

You put the pipe stretcher on the 300 midpipe.. I think with adapters, my board stretcher would do it.. But you'd also need a left handed hammer..

If your Mbomb wasn't cut, would you have been able to tighten the clamp onto the 300 midpipe ? 3/4 inch is good? 1/2 inch, not so much?

You and your hacksaw.. Yall have a thing going on?