Since the first round, when my rev limiter was fooling me into believing I'd screwed up the jetting, I discovered that modifying the end cap was as effective as the $245 FMF slip-on (that I returned) and not nearly as loud. But I freaked out over the jetting (limiter) and welded everything back the way it was.
Well I still think a raised limiter is a good idea, and not sure about no limiter. But I did take yet another crack at that endcap.

I had a nice chunk of 1&1/2 inch tailpipe with a curve in it for the outlet. I used a cut-off saw to cut little slots in it, and replaced the two tiny stock tailpipes with this one. I left the screen spark arrestor in place, all the same as last time, except this time I added an extra baffle, a removable extra baffle.
The extra baffle is a piece of 20 gauge sheet metal about 8" x 10"
wrapped around the spark arrestor screen, kinda like a burrito, not sealed just wrapped, with one screw in it to hold it in place. Then, with the same cut-off saw, I made a series of slots in it, about 30 1/8"x1&1/2" slots. Then I hammered 3/4" of the end over the end of the spark arrestor (toward motor) then slid it off a half an inch, allowing gases to go over, through and around the baffle before passing through the screen, and into the slots in the tailpipe and out. Result, same low end kick as the FMF, and a little quieter than stock. With baffle removed, louder than stock,
a little more low end kick. Removing the baffle is easy, take off end cap, pull out end cap assembly, remove one screw and baffle, replace end cap. Besides doing this 3 times, the only thing I screwed up was that I cooked the gasket that seals the end cap, so it leaks now, but I think that is easily fixed, and doesn't matter much anyway.

I'm going to give this a good hard ride tomorrow on familiar trails and washes. I'll let you know how I like it.

 

Oh yeah, that worked. Great ride today, smooth power all over the place, sounds better, a little quieter. I'm done with that. K&N, end cap job and a 175 mainjet. Didn't hit the rev limiter once.
All I need now is the nerf/heelguard thingamajigs.

I'm getting dialed in with the DS.. I'm just walking away from everybody. This thing is awesome. Only the Raptor can almost keep up with me.. It is just so awesome to go this fast, in total control.

 

Is your airbox stock? Did you drill any air holes in the lid or anything? Just wonderin'...
I've been thinking of a K&N, drilled airbox & the cheap end cap trick.

 

No airbox mods, but just the K&N had me upping the mainjet to 175 from 165. Just the K&N also took me into rev limiter land. So I think the stock paper air filter must really be a POS. If you are handy with a torch or a mig you can mod your end cap pretty easily.
I experimented with it to get the "sound" and performance I wanted.
I noticed that when I had my new baffle in place the first time it was too restricted and was hard to start and keep running. I cut more slots in it and slid it down a little to open up the end as well as the sides, bingo, that gave it the flow and the sound. My Theory was this. The stock twin tailpipes have only about a 3/4" diameter inside the end cap. I replaced them with a 1&1/2" tailpipe. That is twice the area. In order to keep noise in check I added my burrito baffle with 30+ 1/8" x 1&1/2" slots, that's also more flow area than the tailpipe, but a circuitous route to cut sound. I still don't have a digital camera, I'd be more than happy to pull this thing and take some pictures if I did. But I am now (at least for a few weeks!) totally happy with the powerband on this thing, the increased low end really helps out on the rough trails. Low end torque instead of low gearing, I just let the clutch out and thump my way through. Then hit it and scream AY CARAMBA!!
If my DS had been in that Dirtwheels shootout it would have kicked everything's A$$!![img]i/expressions/face-icon-small-cool.gif[/img]
Now as far as the DS being a trailbike, nah, it's a TRAIL ROCKET!!

 

I would really like to see what you did with the muffler and the baffles. This really sounds interesting and if you get a chance, take some pictures and post them or send them to my e-mail. Thanks ahead if you can do this.

 

I just bought a DS650 and am very interested in your end cap mod. Could you post pictures of it? If not some more specific directions would really help. It sounds like the way to go.
Thanks,

 

Okay guys, I don't yet have a digital camera, but I think I can explain it to you. First, you've got to be a welder. You can Mig or oxy/acetylene this. The initial surgical removal of the stock tailpipes requires a oxy/acetylene cutting torch, so I just used a torch for the whole thing. Now remember, I did this 3 times because I got screwed up thinking I couldn't get it jetted right when I was actually hitting the rev limiter in my overzealous pavement jet runs. So I did it, un-did it, then re-did it,,,Duh.
The first step is to remove the existing twin tailpipes. Once you have the end cap off, you can see the tiny 3/4" holes of the stock tailpipes. What you can't see are the small baffles inside these small tailpipes. What you are going to do is replace these two small tailpipes with one the size of the main headpipe after it comes together, about 1&1/2". That's twice the flow area. Now I had some pieces of automotive and ATV exhaust pipe which I used. I chose a piece with a nice bend in it so I could have an exiting tailpipe that turned down and away from my rack, kinda like the stock twin tailpipes did. I started with a nice end cut that would only stick out of the muffler about 3 inches and go into the muffler about 6. So I've got a nice little piece of tail-pipe about 9" long. I close up the inside end of the new tailpipe to about half, and, using a cut-off saw, make about 25 slices in the new tailpipe. Each slice is about 1/8"x1" about 1/4" apart. I then take a punch and push in every other one of the little bridges of metal between the slices, making an irregular, circuitous path for the exhaust. Okay, that's your new tailpipe.
Now back to removing the old twin tailpipes. Using a cutting torch. Wait, first remove the gasket material on the inside lip of the end-cap which seals it to the muffler. I didn't. I cooked mine.
Using a cutting torch, carefully cut out the stock tailpipes. Leave as much metal as you can, and watch out for the spark arrestor, which is the screen cage around the tailpipes inside the muffler.
I left the screen cage attached to the end-cap through all 3 re-tailpipe jobs. Just be careful, when you are cutting out the stock tailpipes that the torch doesn't blow through and waste the delicate stainless steel screen of the spark arrestor. A good cut around the tailpipes on the end-cap will allow you to remove them. A few whacks with a hammer will help. One more demo Item and you are ready to start putting it all together. At the end of the spark arrestor cage is a small oblong cap. I beat it square with a hammer, making it a little smaller, you will need the room for the "burrito baffle" which I used to quiet the DS back down.
Time to install the new tailpipe. Obviously, we have to put a single large circle into a space previously occupied by two smaller circles. First cut out what is in the way, put the new tailpipe in and tack it into place. The first time I cut little pieces of sheet metal and welded them into place, the second time I just filled it up with weld. They both worked.
You now have a more open, little louder, exhaust. In order to quiet it down I took a piece of sheet metal, 8" x 10". rolled it around the spark arrestor, then took it off and cut lots of slots in it like I did the tailpipe, but more. Then I put it back on the spark arrestor, and beat the end down over the little inner cap I'd already hammered square. Then I slid the burrito baffle off the spark arrestor about half an inch and put a screw through it into the little inner cap, holding it all together. The Burrito baffle is just wrapped, with a big gap, and a good 1&1/2" overlap. Gases can escape over, under, through, and in the end and it all goes out the new 1&1/2" tailpipe. What's a burrito know about gases? Right!
It works great. Get creative. I experimented. a little of this, a little of that. Too much, not enough, just right.
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