I will check as soon as I get home in a couple hours.

Here is the screen I am referring too. It caps the end and can not be removed without cutting.

 

Here ya go. 813.05.682.000 model 781

 

Much obliged. Will be in radio silence for a few weeks but will come back to the thread as I move foward.

 

I must not have not been hearing very well when I tried it out, I checked the db's out tonight and was 96 ,Just for grins I put a new gasket into the mega bomb and put the stock can in it .It seemed to fit almost perfectly couldn't detect any exhaust leeks at the connection. put a screen and tip on the pipe and reduced it to 94dbs , It actually has a nice throaty sound ,Still a little loud ,But ran ok ..I'm still running Klxter's recipe for lidless that's why I wanted to open up the stock can a little , Just trying for a little more quiet without sacrificing too much power

 

Here's another view of the inside of a modern KTM EXC style muffler:



Instead of allowing exhaust to flow straight through and out the end cap, KTM dumps the exhaust into an open chamber where the sound waves bounce around and help cancel each other out. Exhaust then finds its way out the end cap which is strategically placed completely out of line with the inlet tube.

 

Doe's anyone have a pic or a link to an exploited view of the stock can?

 

Haven't run across that in my searches. I'd be surprised if the OEM mufflers didn't use a vaguely similar design (chambers). Although, the KLX300R muffler on my bike how with the open end cap is has a grating tone to it. I actually prefer the straight-through sound of the FMF (though neither is anything close to stealthy, like the OEM KTM mufflers achieve).

 

More info on the KTM mufflers. Apparenlty, KTM only packs half of their muffler cans with fiberglass. The other half is shown in the cutaway above.

Here's a thread on ADVrider with a few more pics and info: KTM 450EXC Muffler Rebuild | Adventure Rider

Now wondering if I shouldn't consider adapting a KTM EXC two stroke silencer, the kind that has the angle to it. That would provide a LOT more silenced, perforated exhaust.

 

Removed the OEM KLX300R header and modified OEM KLX300R exhaust this morning. Q4 sounds just about as loud. I didn't gain anything for sure. Maybe a stock 300R end cap would be better.

I found one more possible option:
https://www.dirtwerkz.com/Pages/prod...t/dB_Dawg.html

It's a DB Dawg listed for the 06 YZ450f, part number 8010B. The page says it will fit in a 1 1/8" opening, which happens to be the size of the Q4 quiet core insert. This should shrink the opening down a little more.

 

This also looks interesting but I can't find a vendor for it.