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 Post subject: Classic Bike Silencers
PostPosted: Fri Apr 13, 2018 12:04 pm 
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Joined: Mon Sep 05, 2016 8:45 pm
Posts: 201
Location: Earlston, Scottish Borders
Has anyone used classic bike style silencers? I decided early on that I want to use an alternative to the PMC silencer to give a different look and sound. There appears to be a lot of cheapish Indian chrome silencers available which I'm not too sure about. However, Armours do what appears to be a decent quality stainless steel BSA Goldstar silencer in two lengths https://www.armoursltd.co.uk/product/st ... star-1-12/

Any thoughts and experience of effectiveness of classic bike silencers on Guzzi powered Pembletons?

Cheers, Ade


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 Post subject: Re: Silencers
PostPosted: Fri Apr 13, 2018 12:19 pm 
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Joined: Thu Feb 07, 2013 10:37 am
Posts: 1721
Location: North Norfolk
Hi Ade,
From memory, the stock DBD34 Gold Star silencer was essentially a straight through with a small deflector, which "chirped" on the over run and came chrome-plated.

A number of people have used Moto Guzzi bike silencers - there are aftermarket suppliers in stainless, KEIHAN being the supplier advertising in the Guzzi Club magazine. They "mirror" original cans, but in stainless steel, mirror polished for all manner of Italian machines.

IMHO Supertrap Disc mufflers (used extensively on circuits where a noise limitation is in force) are the best option - small, efficient and as quiet as you like (simply add more discs) without affecting the engine's ability to breathe.

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 Post subject: Re: Silencers
PostPosted: Fri Apr 13, 2018 5:55 pm 
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Joined: Sun Sep 15, 2013 10:13 am
Posts: 547
Ade

I like many(?) other pembelton builders have wasted time and money trying what you want to do

I think ive at least 2sets of silencers in the attic

Basic issues are noise - the pg silencers just get through the noise test, the silencer ends need to be radiused for the test and the mountings need to be test compliant and the correct odd diameter

Id suggest buy or borrow pg silencers for the test then do what you want

Colin


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PostPosted: Sun Apr 15, 2018 9:46 am 
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Joined: Sun Feb 24, 2013 6:56 pm
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I've classic bike silencers on at the moment I'm pleased,with the look they come with a short bar which I didn't use ...will the chrome last I don't know cos only time will tell but seems fine to me
I used a rubber bobbin to connect them to the body so he carnt get his dabber near them.
When I casually guessed max power revs when filling out the forms I said 5700rpm now above 5000revs they check noise levels at 1/2 max revs but say below 5000 revs it's done at 3/4 revs ,now with brooklands I hit 99decibles too close for comfort ...I think 100 is a fail and thesilencers in the pictures hit 75decibels
It's true what you say about wasting money Colin I can see I'm about to waste some on seats trying to get a compromise between what looks right and comfort..for me in the past the two don't always go together as my back seems over sensitive to angles


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PostPosted: Sun Apr 15, 2018 2:29 pm 
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Location: Earlston, Scottish Borders
Thanks for the replies. One of the main reasons I am avoiding the PG silencers is that they are too loud and raspy for my taste. I want to achieve an exhaust note that has presence, but avoids the higher frequency sounds. In my limited experience of silencing technology, this can be achieved by using the straight through, perforated tube approach. I plan to use a two stage exhaust system with a short 20cm silencer up front placed at the primary length (around 90cm) in an attempt to preserve the original Guzzi design characteristics. Then at the rear end an appropriate classic bike silencer.

After discussing this topic with Tom, he decided to add the same short silencer to his system in front of the standard PG silencer. It has made a big difference to the sound volume, which gives me confidence in this approach, but I still don't like the sound the standard silencer produces. I guess I will just have to take a punt on a classic bike silencer and see how it works out!


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PostPosted: Sun Apr 15, 2018 4:26 pm 
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Location: N.Yorks
I found that a forward silencer at 900 mm from the port was not quiet enough for my taste. VW beetle tailpipes fit neatly into the BMW pipes PMC supplies and together with some decibel killers the noise leve is much more acceptable.
More silencer at the tail end means more weight to support...


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PostPosted: Sun Apr 15, 2018 9:28 pm 
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Location: North Norfolk
Ade,
From what you describe, you might do well to emulate the arrangement Dave Parr has on Silverfish - an expansion chamber in each side pipe, shortly after the join with the header, then a straight pipe leading to a "fishtail". I don't know if there's anything else in the system, but the sound is quietly, very vintage.


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PostPosted: Mon Apr 16, 2018 9:56 am 
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Ade,
I spotted "drag pipe baffles 1 1/2"" on display in my local custom bike shop. These tap into the end of the exhaust pipe, labled for a 750cc sidevalve Harley Davidson, are a perfect fit in the PMC mild steel pipes.
I intend using in addition to motorcycle silencers for MSVA test, at round £5 pair worth a try.
Cannot report on effectiveness as Supersport not yet running - hopefully next weekend.

Jack

Supersport 410


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PostPosted: Mon Apr 16, 2018 6:23 pm 
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I have one of each of those, in the tailpipes of my PMC silencers - each "mute" is described as coping with the "bark" of a 1 litre +, motorbike engine. The 2 "mutes" take the edge off the "bark" of my 980cc motor, but not much! The one saving grace is I can take them both out, listen to the "bark" and then put them back in!

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PostPosted: Mon Apr 16, 2018 7:57 pm 
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Location: Northampton
Those so called DB killers are BHP killers too!

You're better off with "proper" silencers with an expansion chamber, perforated tube and sound deadening. The larger OD the quieter, but the perforated thru tube should be the same ID as the standard exhaust.

I plan to have in line silencers after the headers AND cans at the back. My 2cv engine with brooklands cans is almost unbearable.

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If it ain't broke, fix it 'till it is!

Guzzi 750 Supersport 316 - on the road
Guzzi 750 LWB supersport 413 - in build


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