Yes.
Lots more low rpm torque and better gas mileage. It was averaging 37.5 mpg with the stock manifold, and after the manifold averages 39 mpg even with a larger throttle body.

I went to work on the INSANELY loud Delkevic exhaust.




First I gutted the muffler. It had came with "quiet insert" that did nothing. You couldn't tell if it was in or out, so I got rid of it and made my ownout of a washer and some scrap pipe. It's a typical design that looks similar to this.



The outlet diameter is about 75% larger than the stock muffler outlet.





I also added an internal honeycomb quiet insert like this.



It fit the muffler perfectly with no modification. These two mods really quieted down the exhaust. I'll post a sound video when I have time.

 

Here's a sound video of the Delkevic exhaust with quiet insert. It's high and tinny... but I'm happy with WAY quieter high and tinny over INSANELY loud.
This I can live with. There isn't much to expect from such a tiny muffler only 8 inches long, but it's really lightweight and lopped 5 pounds off the bike. Later,I'll post a riding video.

 

An FMF Megabomb header got rid of the high tinny sound. The exhaust sounds quieter more pleasant and mellow now. I'll post a sound video so you can hear the difference. The FMF header noticably produces more low rpm torque which makes the bike that much more user friendly. The chamber is a very clever feature that adds volume to the exhaust and mimics a LONGER torque producing headpipe WITHOUT actually being longer.


The end of the header is slightly flared to accept the stock graphite gasket. I left part of the gasket protuding past the outside the pipe so it could join the pipes without dinging it up. The fit is very tight and doesn't leak. If you want more bottom end pull from your engine I definitely recommend the FMF.

 

Did the washer you welded in quiet it down? I'm running a Delkivic w core on our XT 250, w stock header . Sounds good, but not super quiet. Did wake the bike up a bit. At ~ 400 miles of mixed use, I'm happy with the de-snorkle, drilled baffle on a stock tune. It's been run hard, and the header is a light, golden brown. No indication of lean condition, up to 2400 ft elevation, so far.

 

It did.

The Delkovic exhaust I got is very short at only 8 inches long so I needed to do something. The washer has 4 inches of tubing welded onto it that extends into the body of the muffler. This is a typical design for many quiet inserts so I simply copied what they did.

Although the insert quieted the exhaust, there was still a hard "tinny" edge to the sound. I was pleased when the Megabomb header took that away. FMF claims 1.5 DB reduction in sound and it is noticably quieter.

I'll post a video when I get the opportunity as the difference is striking. I'm totally pleased with the sound as it is now, as well as the generous increase low rpm torque. I'm not interested in high rpm horsepower as I ride for daily transportation. Torque is what makes a bike comfortable to ride at low rpms without lugging the engine. I ran an FMF Powerbomb header on my DRZ400SM and it had the similar effect.

 

Here's a sound clip with the FMF Megabomb header.


The camera attenuates the sound so the difference may not be audible on the video, but in real life there's quite a difference as the header mellowed out the sound considerably.

 

Put a grill in the muffler...

 

This is my latest creation...


It's scheduled to get dyno tested next week. I'll post the results.

 

Dyno test...

 

Thanks. I wonder what the baseline #s were, and what it would pull with the snorkel jerked.