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I did this 2nd version of my stock muffler modification August 28, 2007. I thought I documented it but the were no photos uploaded and they were still in my 2-be-sorted folder. Ooops! I must'a been busy or I got distracted.

This muffler was my original muffler. I have 2. The other previous one came from the generosity of my good friend/comrade Beemeridian who shipped it to me long ago after doing a few things on his OilHead when he visited my home. I cut that one open, drilled all the passageways full of large holes and removed the steel wool packing. After re-welding it and running it on the bike, it was STILL quiet, but just a little tiny bit louder. I know it had to breathe freer, with all the relief holes I drilled. It dyno tested in my NJ shop at 80.3HP.

After reading where someone had removed ALL the internals, I decided It was a good move. I had done just exactly that to the stock muffler of my 1978 XS-750 Yamaha 3 cylinder and it sounded fantastic!! Having a friend with a MIG welder helped a lot.

Fast forward to August 2007 and the full-on mod idea returns. I would mention the name of the local shop that did the welding, but the shop boss that told me he "had the new guy weld it up" ALSO charged me $20 more than the $30 estimate I told him beforehand over the phone the thickness, it was Stainless Steel and the total perimeter length. He also saw it in person when I dropped it off then gave me the estimate. Lightening may have hit his shop since then.

With consideration of our Dial-Up friends, Here are those pictures:
http://i142.photobucket.com/albums/r87/ ... MG9130.jpg
http://i142.photobucket.com/albums/r87/ ... MG9125.jpg
http://i142.photobucket.com/albums/r87/ ... MG9128.jpg
http://i142.photobucket.com/albums/r87/ ... MG9127.jpg
http://i142.photobucket.com/albums/r87/ ... MG9129.jpg
http://i142.photobucket.com/albums/r87/ ... ollow1.jpg
http://i142.photobucket.com/albums/r87/ ... ollow2.jpg
http://i142.photobucket.com/albums/r87/ ... ffGuts.jpg

Anyone attempting this mod needs to realize you'll need about seven 3" high speed cutoff wheels to get thru the outer skin and very thick/heavy pipes inside. The main access hole also needs to be large enough to wrestle the securely welded and encased 3 pipe assembly out the opening . . . . as the pictures show.

Had no opportunity to dyno it again, even though I was there before the PA Bash for a new set of Pilot Road-2's. Oh yes, the sound. It's much louder than before, but it could almost pass for a stock M/C muffler. I do not hear the sewing machine motor as much and it resonates really nice and deep at 2,750 RPM in top gear. Sweet! The exhaust mods are finally over.

EDIT: Added redundant paragraph and one more important pic (MuffGuts.jpg) to the group.

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Good write up, Rob. I've thought of modding my stock can also. I run a Remus CF, so I figured it might be fun to experiment with the stocker. BTW I had a 78 XS 750 also. Bought it new for $1995. Pretty danged good bike.

13

Great job CycleRob...Thanks for the pictures.

Have you noticed any difference in fuel economy?

DJ

The weight. I just weighed the ugly mass of 3 tubes I cut out at 3.0 lbs. Yes, 3 tubes. Inlet, outlet and transfer plus 2 blocking/restraining partitions. It's heavy. It was 3 lbs I don't need that was doing a job I didn't like. It's too bad it's made out of Stainless Steel and was so very hard to cut out.

The MPG. Amazingly, I have no recent reliable data. That, plus in the last 3+ years I have not been keeping track. On my trip prior to the Bash from NJ to NH I ran into 3 traffic back-ups totaling about 20 minutes -plus- cruising speeds 75--80 MPH moving with the traffic in a 70MPH limit. It got 48.0 MPG (28.4km/L) under those conditions, a disappointment to me.

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CycleRob

"It got 48.0 MPG (28.4km/L) under those conditions, a disappointment to me."

Now I just read your statement about how disappointed you were with your fuel economy, and your 28.4 k/litre figure, made my bike appear like a desert camel in heat. (well thirsty at least)

Assuming a US gallon equates to 3.785 litres and 48 miles is the equivalent of 77.24 k's then I would suggest you will be even more disappointed when you revise your calculations to arrive at 20.4 km/litre.

I wish you were correct, as I'd be removing my muffler tomorrow.

Cheers
gunga

Rob

Just curious -- why a gutted muffler vs. no muffler at all?

gunga din,
MPG is our way to measure fuel economy. In the Metric World I've also seen "Liters/100km". Is km/L the widely used or preferred unit (?).
The converter program I used gave the correct answer. I just read 20.4 there and transcribed 28.4 over here

1 mile=1.609344 km
1 Gallon=3.785412 L
Therefore 1MPG=1.609344/3.785412=0.4251436km/L
Converting 48MPG to km/L . . . . 48 x 0.4251436=20.406km/L

To go the other way, 0.4251436/1 = 2.3521464 km/L per MPG
So . . . . km/L x 2.3521464 = MPG

rdsmith3 asked:
"Just curious -- why a gutted muffler vs. no muffler at all?"

No muffler with a short tip is kinda too loud and deposits more exhaust byproducts on the wheel rim. No muffler radically changes the exhaust dynamics from stock. Also, having the stock muffler installed looks better, filling the left case's huge depression for it. My cases are always on the bike. Mostly it was the noise level, which is now just right and still passes the wife test.

Here's another important pic of the muffler surgery.

Anyone attempting this mod needs to realize you'll need about seven 3" high speed cutoff wheels to get thru the outer skin and very thick/heavy pipes inside. The main access hole also needs to be large enough to wrestle the securely welded and encased 3 pipe assembly out the opening . . . . as the pictures show.
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CycleRob

I believe litres/100k is the most widely used metric expression, but being raised on MPG, I prefer to use k's/l; just wish I could get 20.4, my best yet is 18k/l riding freeways.

Cheers Gunga

CycleRob wrote:
Anyone attempting this mod needs to realize you'll need about seven 3" high speed cutoff wheels to get thru the outer skin and very thick/heavy pipes inside. The main access hole also needs to be large enough to wrestle the securely welded and encased 3 pipe assembly out the opening . . . . as the pictures show.

Hey CycleRob,

I know a plasma cutter would be great for opening the exterior of that stainless banana, but could it be used to make any of the internal cuts? I am actually thinking of trying this mod. I have already gutted the cat, and have been satisfied with the results (Slightly deeper note, an almost immeasurable increase in volume, less retained heat after a ride (anecdotal, without emperical data), and a weight loss.) I am wondering how a modestly messaged can would go with the empty cat. Of course, the key is finding a cheap can to work on.

cricman

Doesn't a plasma cutter make a wide cut when it burns thru? (wider than a cutoff wheel). That would be harder to fill in upon rewelding.

As to removing the internal pipes, that should be no problem because you can just keep removing any material in your way. The size of the opening will allow you to go around the internal pipe's circumference enough to keep on removing the rest of it.

Lastly, you should remove no more of the internal piping than I did. It's especially desirable when the outlet pipe is long enough to reach the middle of the muffler. The longer internal outlet pipe length effectively "lengthens" the brief duration of the sharp rise-&-fall of the exhaust pressure pulse, imparting a more pleasant, fuller "boom" sound, that's less of a sharp or shallow "blatt" type sound. I have learned these basics from studying many different muffler cutaway drawings and actually adding extra outlet pipe internal lengths to my Suzuki's custom made 3 bolt removable end caps. Those removable endcaps allowed repeated experimental changes to better tune the sound quality. Longer solid internal outlet pipes were better.
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CycleRob wrote:Doesn't a plasma cutter make a wide cut when it burns thru? (wider than a cutoff wheel). That would be harder to fill in upon rewelding.

It depends on a couple variables: Wear on the electrode and tip, air pressure setting, speed of cut, angle of electrode, and thickness of material. I've made plenty of cuts in 16 gauge sheet that have a kerf as narrow or slightly more narrow than those made by thin cutoff wheels. It is definately faster, in linear inched per minute.

I'm reviving this thread to see if there are any other new opinions out there as to just how good the gutted muffler sounds?

Good timing - check out this excellent How To topic thread concerning R1150GS muffler hack, found over on the ADV board:

http://www.advrider.com/forums/showthread.php?t=244186

At bottom of original poster's message is link to YouTube vid as example of the resulting exhaust note.

Thanks a bunch! The pics are good but the sound on the flic is bad quality even with my new fiber optic net... I would like to hear Cyclerobs take on : $150 worth of SS perf material & SS wool vs. his gut and weld approach to the same job??? And as to using rock wool to stuff the cannister , IMO, it requires periodic replacement in the muffs. that use it?

I gutted mine last year. Mine was more of a hack job than the surgery on cyclerob's muffler. Let me tell you that it sounds way better! It has a growl to it now. Let me tell you another thing. I poured about 5-6 hours of painstaking labor into it as well. I would not have attempted it if I knew how long it would have taken. I also cut about 6" off the end to shorten it up a bit.

Thanks a bunch! The pics are good but the sound on the flic is bad quality even with my new fiber optic net... I would like to hear Cyclerobs take on : $150 worth of SS perf material & SS wool vs. his gut and weld approach to the same job??? And as to using rock wool to stuff the cannister , IMO, it requires periodic replacement in the muffs. that use it?

Yes, wish those muffler sound tracks on YouTube provided better fidelity.

As for the OE muffler hack idea, this ADV thread is inspiring. I'd give it a go if still had the can in the garage, but replaced with ZTechnik some years ago.

If it was me, I would follow the ADV directions until beginning reassembly. Instead of using custom SS perf tube, I would size an inexpensive off-the-shelf SS perf tube (round cross section) with ID/OD to mate with inlet and outlet stubs. The perf tube would either slant inside the can, or could be bent in S-shape at one end (probably the offcenter inlet end) to allow for simple muffler packing. And speaking of packing, I would be tempted to weld up one end of the hacked can, but reconstruct the other end to allow for snug flanged fit, fastened by rivets, as per many aftermarket cans. With such muffler construction, the repacking of can using rock wool is made fairly simple - I actually enjoy repacking mufflers with good quality insulation, as long as the rivets behave!

You're suggesting that after cutting the exit end off(and doing the gut job) you would weld on a narrow strip,say 3/4", to form the insert portion to receive the rivets?

You're suggesting that after cutting the exit end off(and doing the gut job) you would weld on a narrow strip,say 3/4", to form the insert portion to receive the rivets?

Yes, something like that - to create a snug fit for the resulting muffler pieces upon reassembly, and mating surfaces that can be drilled to accept rivets as fasteners.

But really, considering the whole issue of exhausts, weight savings, exhaust tone & dB, and oilhead motor performance, I'd just take the OE muffler off "DJ Downunder-style" and call it good. Put some lipstick on the pig and prevent a drowned catalytic element if you wish with add-on 1.75" tip, or do this:



That's an R1150GS whose owner (proprietor of local independent moto shop) cut outlet off the catalytic collector, rotated a bit, then welded back in place.

There's not much weight saved via the ADV muffler hack (nor for a gutted cat; see http://www.advrider.com/forums/showthread.php?t=38360)). So one or both of these surgeries might reduce back-pressure and increase loudness, but not with any documented torque/power gains.

As for the exhaust "note", my wife's muffler-less R1150R Roadster sounded quite a bit better than my Rockster's ZTechnik y-piped Ti system, at least until the ZTechnik can was restuffed full of good insulation. Even so, my Rockster sounds pathetic compared to buddy's /5 airhead with conventional pipes and double mufflers... his bike sounds about as good as any Boxer motor I've heard. Sometimes regret trading my Rockster OE exhaust for the ZTechnik, although I do like the weight savings.

Lots of exhausting Exhaust talk here on the board... a quick search turns up all sorts of discussion. Example: OE exhaust component weights:
viewtopic.php?f=2&t=17503

And as for performance - have to defer to Oliver and Boxermania for their personal experience with mods. My general take on the subject is that pistons, cams, full exhaust (headers to can), and ECU programming are needed to achieve power gains worth the investment... and even so, I remember someone stating that Type 259 boxer motors are limited by size of intake ports more than anything. But don't take my word for it. All things considered, it might be simpler to run a stock R1150**, and save money to buy a crotch rocket as 2nd bike for trackdays and sports riding.

Yeh, I have read some in the past as you kindly linked and just lately rekindled my urge for a better sound. I have noise induced hearing loss and absolutely don't want a louder bike, even though I wear plugs & helmet always. I'm going to google " how to make a 1150R sound like an early XKE" or maybe "how to make a 1150R sound like a Lotus twin cam" (for under $100) I'm not at all anal about stay OEM, but just like the can on there & don't want to invite the law when passing through a city. I got a loud pipes ticket on a new Triumph TR6 in around 1966 with OEM pipes! Still have a bad taste in my mouth! I will wait until winter when its in the shop,etc..Just plotting for now & I get tempted to bid muffler bling on ebay too then regress to being a tightwad do--it-yourselfer...