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Discussion Starter #1
I got tired of the pile of crap known as a Speedwerx slip-on on my bike. It's had various issues since day one, but recently the case started spider cracking and I decided enough was enough.

Looking at the stock exhaust I realized that the head pipes(roughly 1-1/2 or 1-5/8) are knecked down into a single tube of the same size at the Y. - Obviously, that's a fairly signifigant restriction, thus I decided altering that and a custom muffler was in order to suit me.

I cut the Y aprroximately 1" up from the outlet tube, fitting it perfectly to a section of 2-1/4 exhaust tubing I ovaled one end of in the bench vise.




I then used some sections of a 2-1/4 mandrel bend to mirror the route of the stock outlet pipe, where it turns out past the frame. - I actually used a couple pieces weld together, as everything I used in this build was stuff I had laying around.


Modified the stock heat shield to fit over it:




Y pipe installed back on bike:




I fired it at this point, just to get an idea of the difference. - Drastic difference in tone vs the open stock Y pipe, a lot more mellow and throaty.

I then proceeded to built my own chamber muffler. Since I do a lot of mud & water riding, I didn't want to deal with packing of any kind, but at the same time I wanted to stick with the hi-flow capabilities of a straight-through design muffler, but I also wanted it reasonably quiet.

I started with a 17" section of 4" exhaust pipe and two Vance&Hines 1-3/4" louvered baffles(from one of their harley systems) . I split the 4" tube in half and welded a 3" section of sheet metal in one side(will do the other after the core is complete), giving me a 4x7 oval case. Using the partial case as a template I cut five(5) end caps/chamber walls. I cut holes to fit the baffles in the three internal chamber walls and welded them together. As the pic shows, I ran one straight across the top, the other starting at the bottom and running diagonally to the top(left side is entry, right side is exit, top & bottom as seen). The muffler entry & exit will be at the bottom.



with it in the case - once the end caps are welded on it makes 4 seperate chambers.


I welded another section of 2-1/4" madrel bend on the inlet to the muffler, along with a short section of straight 2-1/4" ID tubing to allow me to slip fit it over the new y-pipe outlet. I welded two tabs on the top and bolted the OE pins on to slide into the mounting hanger. - The slip connection is secured with a SS t-bolt clamp, but I may weld the OE wire tabs on and hook the tension springs on as well since the muffler still utilizes the OE slide pin mounts and isn't directly bolted on anywhere.


I used two 90* sections of mandrel bend on the outlet side, snorkeling it to just below the rear rack. I put a couple triangle cut sections of .090 plate top and bottom to support the snorkel; also drilled a few holes in them to make it look more "finished". I then painted it with 1300* VHT flat-black header paint.

Finished muffler on the ground -


On the bike(I had ran out of paint at this point, it's finished now):







I'm super happy with the end result. It looks good on the bike and the sound is awesome! Really deep/throaty tone, pretty quiet when cruising but sounds mean under acceleration.

***The big plus*** So far I've added a tad over 15% more fuel to it through-out the map and it's still not enough, so obviously the stock Y pipe was a fairly signifigant restriction. The bike was strong before, it's getting to be pure evil now!
 

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Nice work! :thumbup:
Definitely will snork my next exhaust system on my brute.

Sent from my MB525 using Tapatalk
 

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thats awesome and thanks for pics ....
 

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Very inginuitive. Good job bro.
 

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Discussion Starter #10
Thanks guys. - I'm a DIY type of person, couldn't afford my hobbies any other way.


***I should note, the Y-pipe is the major gain here. One could easily just use an off-the-shelf automotive performance muffler(like an ultra-flow, flowdisaster, etc) and still see a big gain from removing the choke point.
 

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Discussion Starter #12
So I had been debating my baffle design, knowing I left some power on the table in favor of being quieter and thinking that maybe a single large pass-tube would mellow the tone even more..........then I had a reason to find out.

I had used material I had laying around to build the above muffler, and the sheet metal was some body work stuff(20ish gauge) which promptly blew-out after a few fast heat cycles when dunked under water. - I went back with a new core design and used 14g steel through-out to ensure a good long lasting muffler.

It's now a single 2-3/8 louvered pass-tube. I built the tube as well this go-round, free-hand slit some holes in the tube with the plasma then set it in a section of angle iron for support and dimpled them in with a hammer & punch.

Partially done louvered pass-tube. I did it basically half one direction, half the other:




all louvers done:

yes, I did them so that it was spiraled:


Pass tube is 10" long inside a total case length of 17". Tube w/ end plates:




Above slid into case:




Then two slanted tabs on each side in center chamber to create "traps" to help quiet sound:


closer view:


That about sums it up. There is an additional plate on each end that directs the flow towards the inlet/outlet, but also creates an additional chamber for some of the exh to swirl back around into to help quiet it a tad more.

The new version is slightly louder than I wanted, but sounds really good. I'll get registered on youtube & get some video/sound uploaded soon.
 

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Discussion Starter #13
Side deal - My OE exhaust gaskets at the heads were over compressed and starting to fall apart. With the big ported heads they over hung the port & head pipe, thus to keep from having a restriction I had trimmed them out with a carbide cutter; being a graphite composite they were never going to last long like that.

I took some .090 soft annealed aluminum plate and cut-out two rings to use in place of the stock composite graphite gaskets. These fit snugly inside the OD of the head port and the ID is even with the size of my exh ports:
 

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Discussion Starter #14
Other good news - I had gotten a new sensor for my wideband and started tuning on this thing. I had to add 5-10% more fuel through much of the MAP to compensate for the much better flowing y-pipe vs the stock system & SW slip-on.
 

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thats pretty cool. I enjoy seeing the custom work.
 

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I understand that completely.
 

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Now that is very impressive lmao that muffler will last longer than the bike :) good job are you going to do something to the inside to prevent rusting?
 

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Discussion Starter #19
I thought about hitting the inside with the same 1500* header paint I used on the outside, but I didn't. Gonna take a long time for just condensation moisture to rust out 14g.
 

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Job well done JP, Keep up the good work and reports.
 
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