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 Post subject: NS400R too loud
PostPosted: Mon Mar 27, 2017 8:34 am 
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Joined: Sun Oct 28, 2012 6:38 pm
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Location: Spielberg, Austria
Today I had the registration check with my NS400R (German bike, so it needs a special check).

Everything fine - just too loud with standard exhaust.
103dB@4500rpm :smt018
More or less what I have expected, it was quite loud during the test ride yesterday :mrgreen:

No registration in Austria until I have solved this issue (95dB is allowed)

As far as I know this is a standard problem of the NS400R.

Anyone here who has already disassembled some stock NS400R exhausts?
Is it necessary to cut them to open it?
Which technology are they? Resonance dampers or absorption dampers?
What`s the reason why they get so loud?

How can I get them a bit more silent (at least for the check)?
After the check nobody will care about it...

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My bikes:
RD500 YPVS 1GE
RD350 YPVS 31K 1985
Honda NS400R NC19
Honda CBR 1000 RR SC57
Yamaha R1 RN04


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 Post subject: Re: NS400R too loud
PostPosted: Mon Mar 27, 2017 10:18 am 
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any thought in changing the counter sprocket by going up a tooth or two. A few years back in California. The 67 911S was tested at a smog shop. It needed to be at the correct rpm for the engine to be at a correct load. The wheels where 15" all the way around. The owner changed the rear wheels to 14" so the power will be at the correct rpm. the 911 looked funny 14" in the back and 15" in the front. It passed smog.

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1996 RGV250(Lucky Strike)
1994 MC28SP
1995 MC28SP
1996 MC28SP
1985 RG500(Walter Wolfe)
1984 IT490
1985 RZV500R
1985 NS400R
1985 NS400R
1997 VFR750
1992 FZR1000
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 Post subject: Re: NS400R too loud
PostPosted: Mon Mar 27, 2017 11:30 am 
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Thats a pisser...These guys may be able to provide a temporary fix for the test, have a look..

http://www.decibeldevil.co.uk/

Out of interest, I found , from my NS's(I had 2 at one stage) and friends NS's, the first batch of (1985) bikes that came into the UK where louder than the 1986 bikes, I actually got stopped by police on my '85 NS back in the day because of the noise, the police thought id fitted aftermarket pipes at first, then accused me of tampering with them, which I hadn't.


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 Post subject: Re: NS400R too loud
PostPosted: Mon Mar 27, 2017 1:10 pm 
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Location: Quebec city Canada
I would try some restriction in the headpipes maybe with steel wool or a washer for a smaller aperture .


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 Post subject: Re: NS400R too loud
PostPosted: Mon Mar 27, 2017 2:20 pm 
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As far as I found out this was a problem from the beginning that they were too loud after 10000km or so.
I`m expecting that they are absorption dampers and the wool inside the dampers is burnt or full of oil and soot.
That`s why the modern bikes all have this massive reflection dampers (without wool inside), they don`t change the noise level over time.

Maybe they already made changes in 1986, but there it also seems that it was not a final solution (and then they stopped the production).

Thinking about refurbishing the end cans or to put some inserts/washers in front of the end cans to reduce the noise for the check.

By the way, it`s not driving noise, it`s just measured in a distance of ~1m 45° angle from the rear of the bike.

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My bikes:
RD500 YPVS 1GE
RD350 YPVS 31K 1985
Honda NS400R NC19
Honda CBR 1000 RR SC57
Yamaha R1 RN04


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 Post subject: Re: NS400R too loud
PostPosted: Mon Mar 27, 2017 3:29 pm 
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You need to cut the silencers open to repack them. Not a good solution.http://www.ns400r.co.uk/forum/viewtopic.php?t=3188

For a simple solution you can remove the silencers and stuff insulation inside the inlet pipes. That should quiet them enough to pass. Trailer the bike to the test location. Go home and remove the insulation.

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1985 RZ500
1985 RZ500 Project Bike
1986 RG500 ATR
1986 NS400R
1987 TZR250
1988 Honda RC31
2007 DL650 VStrom
2014 Triumph Thruxton Modified


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 Post subject: Re: NS400R too loud
PostPosted: Mon Mar 27, 2017 4:28 pm 
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My friend has DEP silencers on his 400 and they are quieter for sure...and re-packable...

http://www.deppipes.com/product-listing ... ncers/file


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 Post subject: Re: NS400R too loud
PostPosted: Mon Mar 27, 2017 4:43 pm 
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Thanks for the information.
Inspected them and they are full of soot...

I already removed the end cap of one silencer (3 welding spots).
Not a real success as the inner can is again welded all around.
If I choose this option this would mean:
- Removing the end cap (3 welding spots)
- Removing the outer beauty cover to get to the inner weld (~10 welding spots/lines)
- Removing the inner end cap (one weld all around)

Don`t know if it`s necessary to remove the front plate.
Doesn`t look like it`s welded from the outside so maybe not needed (on the upper silencer)
The lower silencers also have a band around the front end which is formed to it`s shape after positioning - if this has to be removed again 2 or 3 welding spots have to be drilled and a slot in this band is needed to get it off.

A lot of work, but not impossible to get them back to stock look later in refurbished condition.
Maybe also possible to make some "maintainable" end cans out of them - the affected area is completely covered by the beauty covers.
Maybe a project? Damn... I have to finish my RD500 :smt013


Reducing the diameter of the exhaust is also not a really good solution.
Turned some washers to the right diameter and inserted them between the pipe and the silencer.
Diameter is reduced to 8mm, but no real effect on the sound - only the left cylinder doesn`t want to run anymore (maybe because the bike was started 10x today but never more than 2min... Needs to be warmed up completely again)

I will probably go for the insulation method only for the check...
Going to the check place isn`t a problem, it`s anyway in my van as I have no registration.


But I need a solution for later, the bike is really loud and if there is a Policemen whose wife was mad on the day before it can get expensive...


By the way, this bike is really loud without end cans, even in idle :smt005
Maybe one of the loudest I have had in my garage up to now :smt003

_________________
My bikes:
RD500 YPVS 1GE
RD350 YPVS 31K 1985
Honda NS400R NC19
Honda CBR 1000 RR SC57
Yamaha R1 RN04


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 Post subject: Re: NS400R too loud
PostPosted: Mon Mar 27, 2017 4:50 pm 
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podman wrote:
My friend has DEP silencers on his 400 and they are quieter for sure...and re-packable...

http://www.deppipes.com/product-listing ... ncers/file


Are they road legal (EG number)?
Otherwise it would get more complex and expensive...

_________________
My bikes:
RD500 YPVS 1GE
RD350 YPVS 31K 1985
Honda NS400R NC19
Honda CBR 1000 RR SC57
Yamaha R1 RN04


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 Post subject: Re: NS400R too loud
PostPosted: Mon Mar 27, 2017 5:08 pm 
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Talk to Ian at CRR. If anyone has a solution, it would be him. http://www.classicracereplicas.com/Hond ... haust-664/

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1985 RZ500
1985 RZ500 Project Bike
1986 RG500 ATR
1986 NS400R
1987 TZR250
1988 Honda RC31
2007 DL650 VStrom
2014 Triumph Thruxton Modified


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 Post subject: Re: NS400R too loud
PostPosted: Tue Mar 28, 2017 3:22 pm 
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Location: Veendam, the Netherlands
Der meiste Laerm bei 3500 rpm wuerde der hintere cilinder geben, also der obere auspuff, der hat kein ATAC. Ich kenne kein endcans die leiser sind als die original, DEP (habe ich selber, obere ist am lautsten und lauter als standard, hat auch kein zulassungsnummer) und Swarbrick sind lauter
Ich wuerde zum test der obere daempfer abbauen und mal sehen ob da mal ein Selbstgebauter DB killer reinmachen , perforierte huelse mit, mal links dann rechts ein schott machen. Probieren kann man es ja! Alles ëingetragen, die huelse wieder raus. Oder der zuendkerzenstecker abziehen von obere cilinder..... :smt006


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 Post subject: Re: NS400R too loud
PostPosted: Tue Mar 28, 2017 4:06 pm 
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Location: Veendam, the Netherlands
Or something like this, looks shite.....
Image

:smt020 :smt017 :smt006 :smt014 :smt005 :smt013


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 Post subject: Re: NS400R too loud
PostPosted: Tue Mar 28, 2017 4:09 pm 
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Joined: Mon Nov 16, 2015 1:41 pm
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Speed Freak wrote:
podman wrote:
My friend has DEP silencers on his 400 and they are quieter for sure...and re-packable...

http://www.deppipes.com/product-listing ... ncers/file


Are they road legal (EG number)?
Otherwise it would get more complex and expensive...


No problem with a UK MOT test but they are pretty slack on the noise front, I suggest you contact DEP for a definitive answer.

Good luck with a solution anyway.


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 Post subject: Re: NS400R too loud
PostPosted: Tue Mar 28, 2017 4:22 pm 
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Joined: Thu Mar 09, 2006 12:54 pm
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Location: Germany
Ok, here's a German engineering high tech cheat device I used to calm dow the carbon Shark exhausts on my VTR:
http://www.vtr1000.de/forum/showthread. ... ght=Klappe
(Basically all manufacturers use it nowadays to cope with noise emission laws)

What you could do is to manufacture a drum with a hole acting like a power valve between the stinger and the can. Using a butterfly would also work, but maybe needs more length to be inserted.

The Ignitech STPS can control the opening/closing TPS dependent, i.e. you can program it to staying rather closed at noise testing (low TPS, high rpm) and open at normal operating conditions (high TPS).

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 Post subject: Re: NS400R too loud
PostPosted: Tue Mar 28, 2017 6:35 pm 
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Not much time today to work on the NSR...

Found out or at least found it somewhere in the Internet that in the resonance chamber they also have a perforated sheetmetal with wool behind.
From the carbon deposits in the stinger I think there is no perforation anymore :smt003
So there are basically 2 problems per cylinder if I want to get it down to 95dB only with restoring the original parts (I think not possible)...

Burning out all the carbon will lead to burning out the wool also... Will not have much effect then :smt018


I tried again to make some washers (8mm diameter) in the stingers, last time I think one did not stay in the place where I wanted to have it.
Anyway, not really much effect - from the feeling the lower right is the loudest :smt017
Lower left has not much pressure, I think the carbs are also not 100% sync as it stays a bit colder than the right one.

Then I stuffed something into the Silencer ends (shredded paper) just to see the effect but it was not like I expected...

Tomorrow I will take off the fuel tank and check if the air filter is standard.
I remember my NSR125 where I put a mushroom filter on for testing - it was incredible loud and the behaviour was quite the same.
At idle and with throttle closed it was not loud, but when I opened the throttle it was incredible...
It was also a common thing to remove the rubber inlet snorkel from the air filter case to make it louder.
Maybe it isn`t a problem of the exhaust.
Let`s see tomorrow...

By the way, I was riding my RD350 today, there is not much difference to the Honda, even below 7000rpm (should have 99dB, everything is stock including the inserts in the pipes)

_________________
My bikes:
RD500 YPVS 1GE
RD350 YPVS 31K 1985
Honda NS400R NC19
Honda CBR 1000 RR SC57
Yamaha R1 RN04


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