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Old 02-18-2013, 07:21 AM   #1
Sabre170 OP
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2 to 1 exhaust

I have a '78 100/7 that I'd like to convert my exhaust to a 2-1.

Sadly, I don't have the ability to manipulate metal to make my own pipes. I'm fully aware of the MAC pre fab'd 2-1 exhaust, but have had no luck finding any other pre-fab'd ones.

Does anyone have any other suggestions?
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Old 02-18-2013, 07:51 AM   #2
100RT
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I'm curious as to why you want to go that route. I wish I could convert my 1150RT to dual exhaust so it sounds like a motorcycle. My 81 R100RT sounds much better.
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Old 02-18-2013, 08:56 AM   #3
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Well, it is kinda a 2 fold answer, but honestly, mostly cosmetic. I converting the /7 to have more of a cafe look/feel to it. As part of that, I'm trying to "clean up" the bike as much as possible. (I.e. I removed fender, turn signals, ect). I figured that going for a 2-1 would help with that.

A secondary goal of the 2-1 was I was hopping to get a bit more aggressive/throaty sound out of it. The current exhaust/muffler is pretty good at doing its job at muffling the sound.

However, from what you are saying, a 2-1 will be counter productive to my secondary goal. Maybe a 2-1 header isn't my solution, rather keep my current header but put on a cleaner looking (smaller?) set of mufflers on that will also give the resulted sound???

Thoughts?
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Old 02-18-2013, 09:24 AM   #4
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I'm sure the cafe group would say "go with peashooters" like Hoske,There are probably many different brands . I think EPCO has stainless steel ones available called sport mufflers.
http://www.youtube.com/watch?v=KPPQlT8iOiE

BMW R100 - Megaphone exhaust - YouTube
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Old 02-18-2013, 10:09 AM   #5
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Another muffler set is called
Dunstall Decibel mufflers | eBay

Made by EMGO
Amazon.com: emgo muffler
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Old 02-18-2013, 11:38 AM   #6
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Thanks! I really appreciate.

I really like the looks and sound of the exhaust in the second link you posted. The R100 with the "shorty" megaphones. I, thinking that will likely be exactly what I'm looking for.

Do you know off hand what size header pipes my '78 100/7 would have on it? I'm out of town for the next week and can't measure my bike. I want to say that the muffler would need to fit a 38mm manifold pipe, but 40mm and 42mm are also rattling around in my brain as possibilities.
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Old 02-18-2013, 11:29 PM   #7
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Quote:
Originally Posted by Sabre170 View Post
Thanks! I really appreciate.

I really like the looks and sound of the exhaust in the second link you posted. The R100 with the "shorty" megaphones. I, thinking that will likely be exactly what I'm looking for.

Do you know off hand what size header pipes my '78 100/7 would have on it? I'm out of town for the next week and can't measure my bike. I want to say that the muffler would need to fit a 38mm manifold pipe, but 40mm and 42mm are also rattling around in my brain as possibilities.
38mm or 1 1/2"
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Old 02-19-2013, 07:36 AM   #8
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Houseoffubar made me this



...out of pieces from these guys: http://www.coneeng.com/
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Old 02-19-2013, 12:11 PM   #9
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Originally Posted by Airhead Wrangler View Post
Houseoffubar made me this



...out of pieces from these guys: http://www.coneeng.com/
I'm in the process of copying that setup. Keep getting sidetracked on the honey-do list...
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Old 02-19-2013, 09:22 AM   #10
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The 2-1 exhausts from SR-racing are quite popular over here in Germany.

http://www.sr-racing.de/anlagen/BMW/R100GS.jpg

No one has ever complained about performance, in fact they give a rather significant boost over the complete rpm range.
However, I would not use them if classic looks were important.

Regarding the second crossover tube of the post '81 models: I have a technical article where the authors (engineers from zeuna staerker, the company that developed and manufactured the BMW exhausts then) describe the effect of the crossovers as follows:
- The first crossover improves low-mid rpm torque
- The second crossover improves mid-top rpm torque.

My dyno runs have shown this exactly.
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Old 02-19-2013, 09:56 AM   #11
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Originally Posted by RGregor View Post
The 2-1 exhausts from SR-racing are quite popular over here in Germany.

http://www.sr-racing.de/anlagen/BMW/R100GS.jpg

If I'm not mistaken I think SR racing also make siebenrock's exhaust systems don't they?
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Old 02-19-2013, 11:03 AM   #12
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Originally Posted by Airhead Wrangler View Post
If I'm not mistaken I think SR racing also make siebenrock's exhaust systems don't they?

You are right AW its the same as the siebenrock system.

The system is not a big improvement on a stock 800 engine. The bike will loose bottom torque.
But with some engine tuning the system starts to work.
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Old 02-19-2013, 03:43 PM   #13
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It seems everyone is comparing the SR pipes to the stock setup. That I am not interseted in. Almost any setup is going to cost you some bottom end power over the stock setup with a stock engine. What would be intersting is to hear how they compare to other types of aftermarket setups. As far as welding up my own two into one setup for my bike? There are just too many variables and I don't have the dyno and the time to figure out collector shape and length. How far down the pipes does the collector work best, etc.. I could surely copy some that I hear work real well over other aftermarket setups. Personally, I think I am going to stick to two into two's just for tuning simplicity. Plus I have decided that I am not going to go looking for TOO much more through the exhaust because I know from experience that the big gains are going to be LOUD and I am now too old for LOUD. That and now there are a million Harely's out there and almost all of them are LOUD. I don't want to be a part of it.
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Old 02-19-2013, 10:53 PM   #14
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Originally Posted by supershaft View Post
It seems everyone is comparing the SR pipes to the stock setup. That I am not interseted in. Almost any setup is going to cost you some bottom end power over the stock setup with a stock engine.
No, not necessarily. The engines I know (with the SR exhausts) have more low end torque than stock airheads have at their peak.
But this of course may be due to the other modifications. Including cam.

Quote:
Originally Posted by supershaft View Post
What would be intersting is to hear how they compare to other types of aftermarket setups.
Now, these guys did some cross comparison (e.g. to the exhausts from this guy here
http://www.rs-haslauer.de/tuningteile_bmw.php ).

And the answer is that there is no definite answer.
Although the engine specs were similar the engines responded differently to different headers (crossover/no crossover) and mufflers.
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Old 02-20-2013, 12:56 AM   #15
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Originally Posted by RGregor View Post
No, not necessarily. The engines I know (with the SR exhausts) have more low end torque than stock airheads have at their peak.
But this of course may be due to the other modifications. Including cam.



Now, these guys did some cross comparison (e.g. to the exhausts from this guy here
http://www.rs-haslauer.de/tuningteile_bmw.php ).

And the answer is that there is no definite answer.
Although the engine specs were similar the engines responded differently to different headers (crossover/no crossover) and mufflers.

Rudi, how easy is it to get away with a non stock exhaust in Germany? Do people run what they like and then go back to stock when the bike needs its inspection?
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