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Yes obviously I understand that.
It is my belief that the local council here have set the db figure for any modified exhaust deliberately low (ridiculously low in fact) to frighten anybody who would attempt to a modification.
The only other thing to do to alleviate this issue is to try a baffle/silencer 🤷‍♂️
 

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Ok another stupid question for which I’ll apologize in advance for.....
My standard stock exhaust is one piece and has the downpipe coming out of the rear of the cylinder head, down roughly parallel with the rear shock, then bends outwards below the swing arm and into the front of the silencer/muffler.
I’m told that the CAT is fitted inside the front end of the silencer.
However, every 2-part aftermarket exhaust has (what I’m told is) an EXPANSION tank positioned 1/2 way down the downpipe?
So, if the stock system doesn’t need this, why do ALL the aftermarket exhausts I’ve ever seen have it??
2nd question..... will the lack of a CAT damage the engine??

Geoff,

If you look at the photos I uploaded you will notice that there is No Expansion in the tube. It is on the SS version only.
If you get the Carbon Fiber version, there is no expansion in the tube. I am not sure, but I think the expansion chamber is empty and you have to purchase the CAT that goes in there. It will still fit your bike. I would just gett the CF version unless you really need the SS.
SS Version.png
Carbon Fiber Version.png
 

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The CAT is only fir emissions and will not hurt you engine. If you notice, the O2 sensor is BEFORE the CAT Tube.
 

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Discussion Starter #24
.... so WHY does just about every aftermarket exhaust have an expansion tank on the vertical part of the downpipe, when my standard exhaust downpipe doesn’t have one???
Does anybody know why this is?


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.... so WHY does just about every aftermarket exhaust have an expansion tank on the vertical part of the downpipe, when my standard exhaust downpipe doesn’t have one???
Does anybody know why this is?


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I thought it was only for two strokes to 'pull' more fuel and air into the cylinder.
 

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The expansion in the 2-stroke exhaust is for the still burning fuel/air mixture to expand while being exhausted. You do not have this situation in a 4-stroke. It is not an expansion, it is for the optional CAT to be installed for certain Euro compliance.
If you look at the exhaust pictures from post #22 and hit expand, you will see that the SS version has the expansion and the CF version does not.
I do not know what exhausts you are looking at but the Yoshimura R-77 has no expansion. Same for Remus. If you do not want the expansion, get the Akrapovic Carbon Fiber.
Racing Line (Carbon)
S-B3R1-RC/1

If you want Stainless Steel, get the Yoshimura R-77
 

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Discussion Starter #27
Excuse my ignorance on this, but why are stainless exhausts different to carbon exhausts , and having said that, how the hell are you supposed to fit a CAT 1/2 way along an exhaust downpipe with quite sharp bends in the pipe either side of it, AND being before the oxygen sensor?
What am I not understanding here?


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Excuse my ignorance on this, but why are stainless exhausts different to carbon exhausts , and having said that, how the hell are you supposed to fit a CAT 1/2 way along an exhaust downpipe with quite sharp bends in the pipe either side of it, AND being before the oxygen sensor?
What am I not understanding here?


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The cat is not fitted there, that's only an expansion portion.
 

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The CAT Inser goes at the end of the pipe BEFORE muffler. See photo.
CAT for SS Version.jpg


Why it has the expansion, I do not know other than to maybe compensate for the additional back pressure the CAT will produce or to give the exhaust gases more time to pass through CAT. I think you have to buy the CAT separately in order to meet "EC" approval. Will not work with Carbon Fiber model. It is all there on Akrapovic website.
 
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