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New member, thanks for the add. I have aquired thru the magic of eBay, what I thought to be an economical choice (they were dirt cheap) for my 68 a65tbolt project. Wassel dunstall replica mufflers was the ad and the pics showed that. What I didn't notice was there is zero guts. Aka no baffle. And there isn't any sign they ever contained one. No old welds no bolt or rivet holes just a bit of surface rust in there. I'm assuming they're race pipes. Question is has anyone heard of rebaffling pipes like that in an economical way. They kind of curve in to 70 mm at the "mouth" and any baffle going in there would sink in substantially to where the taper is again 70mm. #adultjigsawpuzzles. Or should I be looking for new pipes. I don't relish the idea of tuning giant straight pipes.


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Not answering your question but I have a pair of genuine Dunstall power mufflers suitable for A65. Just in case you would want the opposite from cheap.

Last edited by Morgan aka admin; 09/18/21 7:05 am.

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Nothing wrong with the Dunstall copies if you like the look of them. But they lack back pressure and that will keep you in a lower gear, revving the bike
Trying to get somewhere.

You could Block off some of the outlet tubes or tack weld in some smaller tubes


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68’ A65 Lightning “clubman”
71’ A65 823 Thunderbolt (now rebuilt)
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I run those dunstall copies on my t'bolt, they do need at least 1 exit hole blocked off really.
Just put a plug in one with some jb weld, been there for years.
I just put some wadding gear in them to mute the crackle too, available at trials/scambles shops.
My one also wanted a 250 main but i have larger inlet valves too so that will contribute.
They work well and the old iron will still do the ton with a little persuasion.

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There's nothing in there, no six shooter, nothing. Price was low and typically I got what I paid for. I appreciate any advice and I realize with a sufficient infusion of in the words of Roger Waters, "pounds shillings and pence" anything can be fixed or fabricated. And race guys don't generally ADD baffles, just trying to fix a mistake. Already know the previous owner/ builder put some kind of megacycle cam in there to challenge my meager tuning skills,. So this was what I would call antiprogress. Just when I finished wiring everything except the ignition (lad had a Boyer in the crates so stock harness becomes some what obsolete)


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Ahh, you will wake the neighbours up with those on there.
You can stick some triumph mutes in the end of the header pipes, they
are readily available.

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The original Dunstals ( I have a couple of pairs ) had a tube of punched plate welded to the back of the end end piece / baffle holder which was th same diameter as the parallet section of the muffler so it was supported at both ends
The outlets on the other side are 7 short pieces of tube
The 6 outers are open and the middle one has a nut welded into it
They came with round plates that went under the bolt & blocked off some of the outlets
From memory one had 3 holes and the other had 2 on one side so you could move them to select from 1 to all 6 outlets thus making the back pressure "tuneable"
Around the Sydney CBD the 2 outlets seemed to work best and the one time I tried to find what worked best on the open road, the blanking plates ended up somewhere along the Bells Line of Road


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some Universal Baffle (Stainless Tube)
and "ceramic wool" held on with stainless wire
[Linked Image from xs650.com]

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Yep.
Exactly what my originals looked like from new only no fiberglass wool and as previously mentioned the tuneable end.
The latter cheap ( MCA ? ) dunstal copies had all 7 holes open fiberglass wool & were a fair bit shorter .


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Originally Posted by BSA_WM20
The original Dunstals ( I have a couple of pairs ) had a tube of punched plate welded to the back of the end end piece / baffle holder which was th same diameter as the parallet section of the muffler so it was supported at both ends
The outlets on the other side are 7 short pieces of tube
The 6 outers are open and the middle one has a nut welded into it
They came with round plates that went under the bolt & blocked off some of the outlets
From memory one had 3 holes and the other had 2 on one side so you could move them to select from 1 to all 6 outlets thus making the back pressure "tuneable"
Around the Sydney CBD the 2 outlets seemed to work best and the one time I tried to find what worked best on the open road, the blanking plates ended up somewhere along the Bells Line of Road

Do you have any photos?


Now let’s all have a beer beerchug

68’ A65 Lightning “clubman”
71’ A65 823 Thunderbolt (now rebuilt)
67’ D10 sportsman (undergoing restoration)
68’ D14 trials (undergoing transformation)

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I will have a ferret around Al
I did take some photos of them and post them , but that was via photobucket so probably lost by now .


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OK Al
The hernia is playing up so I ferretted around down stairs & found a set
Note there were several different Decibels and even more than 1 tuneable style decibel
Some had bolt in bafels while others had welded in baffels

So the first 2 just show the name tag & stampings

[Linked Image from i.postimg.cc] [Linked Image from i.postimg.cc]

Next is the business end of a fully welded muffler
The bolt is very well rusted in so I did not remove it and as previously mentioned the blanking off plates are long gone
Note the 3 dimples , these are welded onto some stand off then the the end plate of the baffle.
Also note no light so they are not a direct strait through outlet like the "looks like" MCA copies

[Linked Image from i.postimg.cc]

Next we have a dead one
The bolt has fallen out leaving only the 3 spot welds to hold it all together
The middle of the external end plate has broken off leaving a pretty scolloped hole , note the end of the baffel plate is solid and the hole up the top where the stand off was once welded Note also the thickness of the center tube which is threaded so the bolt actually does the hard work holding the baffel end plate and the muffler end plate together .
The sort of strait line you can see in the middle of the threaded tube is what is left of the perforated plate baffel tube

[Linked Image from i.postimg.cc]

Same end as before but at an angle so you can see that the center tube is proud of the baffel end plate.
So the exhaust has to pass through the punched plate then run along the sides of the muffler then do a 90 deg bend to pass down between the the two end plates before finally exiting via how many holes that are open.
Also note the void around the muffler end plate which id generously cupped supposedly to to provide a smother change of direction
[Linked Image from i.postimg.cc]

Because not even I can follow what I say a quicky sketch not fully detailed or to scale
[Linked Image from i.postimg.cc]

This style tends to fracture the punched plate tube at the restrictor and become very rattley
Then some time latter the rest of the baffle breaks away if the bolt in not in tight but will eventually end up failing as per the above photos


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And a little note about restricting the ends of the cheapie copies
The end plate is not strong enough to take a lot of spirited riding and will fracture allowing the mufflers to become a reasonable hand held rocket launcher firing the baffel out the back with considerable velocity usually to the detriment of whatever is behind you at the time
So if any one is thinking about turning copies into tuneables then you must strengthen the baffle securing which is best done by rivetring an angle bracket between the rolled lip at the far end and the anchor plate bolts


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i like the way Dunstall misspelled " decible"


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Thanks for the info Trevor, I have 3 different types of Dunstall, none of which the decibel type though (some Similar but different) and the Dunstall power which is a solid pipe through an open mega, but with room for gasses to pass down the outside and then escape at the end of the plate (I’ll try and find a pic)

The other two are like the copy cat type above, yet both have been marked up with the usual Dunstall stallings (one is so faint due to being re-chromed) the other type some one cut them so they could fit a smaller pipe) photos are limited as my whole house and garage is in a lockup. The apart from the style of the outer, the only Real difference is the size of the tubes at the back. The one which has been cut to fit smaller downpipes has a smaller outlet at the back. On this is drilled out the pop rivets and knocked the baffle out. Both this and the other silencer have a disc made of perforated steel down about half way down. And of which at some point someone had stuffed with Brillo pads or something similar.

The one I have on the bike currently I knocked the disc out and tapped a smaller size tube down the silencer. It works fairly
Well with it but without intention made it a lot noisier.


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68’ A65 Lightning “clubman”
71’ A65 823 Thunderbolt (now rebuilt)
67’ D10 sportsman (undergoing restoration)
68’ D14 trials (undergoing transformation)

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I have a funny feeling that no two batches of Dunstall exhaust were actually the same
I had a set on the A10 and they were a touch on the noisy side but then again I was 17 & noisy was good then
That bike was a horrid mix of long & short stroke pars running 11:1's ( when it actually did run ) but did so very very fast
However he high compression did to the early thin flange barrels exactly what you would expect it to do and I never managed to get it running again as by that time I has several invitations to have an ( expensive chat ) with a magistrate ( it was a very very fast bike ) .
The A 10 one were virtually strait through.
Decades latter the A65 go the spare set I bought for the A 10 ( for the purpose of passing a reg inspection ) but they were gone inside & did not last long.
Got a couple of sets of the tuneables quite cheap and eventually got Overlander to make me a pair in stainless which the bike still has on along with a customised LH pipe so I can get the the primary chain adjuster .


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