My S40 came with a Jardine already installed but I never really cared much for the sound from it. It was a bit too loud and it sounded like a lawn mower with the muffler rotting off of it. Too "poppy" with not enough "tone". I also tried a Harley muffler I picked up for $5 at a local shop but it too was very loud and had too much blatting popping noise to the exhaust note (although it was better than the Jardine). The best was the de-baffled stock pipe (it was pretty smooth sounding and not too loud) but the VERY noticeable loss of power compared to the other pipes was not OK with me.
I figured out a cheap easy way to fix my conundrum though. I essenntially converted the Jardine from a straight through "glasspack" style muffler to a chambered muffler. It's pretty simple and doesn't take much skill, money or time. Just the way I like it.
Remove the core/baffle from the exhaust and remove the packing material from around the core (if it hasn't all burned up and blown out yet). You will probably have to remove the muffler from the bike so that you can pop the core out from the inlet side.
Plug the core (the tube with all of the holes in it) at the inlet side (side closest to the engine when installed). The inlet side tapers down from the large dia that fits into the pipe to the core dia. The outlet side is more like a plate welded to the end of the core (no taper). I used a thick washer I had laying around (needs to be about 1.5" outside diameter). To plug the hole in the middle of the washer I took the lazy way out and simply put in a short bolt with a nut. The ambitious fabricator will weld this hole shut but like I said, I took the lazy way.
Weld the washer to the core so that it can't come loose. It doesn't have to be air tight but you don't want it coming loose and rattling around in the muffler either. This is the most difficult part as it does require a little welding.
Next, drill holes in the tapered area where it reduces from the large OD (the part that fits snug into the pipe itself) to the core diameter.Be sure to drill at the inlet side (the side you plugged). The size and number of holes will determine how well the muffler will flow and how loud it will be. I figured it up and (4) 1/2" holes have the same area as a 1" thru hole and (9) 1/2" holes are the same as a 1.5" thru hole (roughly the same size as the stock core dia. I drilled (8) 1/2" holes in mine and it's right about where I want it; a touch loud but still quieter than the Jardine was before. I started out with (4) 1/2" and (4) 3/8" but I wanted a touch more flow. Start out small as it's real easy to enlarge the holes but much harder to shrink them.
After that just reassemble. Be sure to rivit or bolt the core back in or it
will work it's way back out.
I was VERY happy with the results. It now has a MUCH smoother sound with more "tone" and FAR less of that Popping single cylinder sound. It sounds more like 1/2 a Harley than a mower with no muffler. There doesn't seem to be any loss of power either.
As a bonus, there is no packing to burn up so it shouldn't ever need any more attention.
Sorry I don't have any pics but I did model up a quick CAD model to better illistrate what I'm talking about (yes, I'm a nerd I admit it).
Hope this helps