Dunstall Replicas - 1971 OIF T120R

[Bloodknot]

…………….Second, the plate tack-welded midway along the perforated core is not solid but drilled with lots of teensy holes (see photo). I can't recall whether people have said their older Emgo Dunstalls had a solid baffle but for some reason I had thought so...……………….

The originals were certainly perforated.

 

[NM Bonny]

The originals were certainly perforated.

Okay, thanks.

I pulled the core from one of them and indeed the wrap is fairly thin (and tends to fall apart as you handle it), and not all the way down the core--though there isn't much room toward the front where they stopped wrapping. But as you can see, the size of the flange for the studs limits the thickness of material you can wrap around the core to considerably less than 1/2".

However, I think Acousta Fil and similar stuff is supposed to expand a little and isn't so delicate, so I still plan on putting in better material.

The perforated disc is smack in the middle of the core's length. But the holes in it are so small that as discussed much earlier in this thread, they seem to intend the gasses to be forced through or around the wrapping to some degree.

I'm still very tempted to try running them with no wrapping at some point, which would make them function like the vintage Sporty mufflers I'm using on my '51 FL. Those are a strictly metal baffle design--perforated core with disc midway down--but my reproductions (made by Gasbox) have a single large hole drilled in the originally solid baffle to flow more as needed for my 74" engine (and sound considerably louder).

Regardless, I measured the outlets: 1" on the OEM cans, and 7x.625" on the Dunstalls. So, the total area of the outlets are .7854" for OEM, and 2.1476" for the Dunstalls.

New unbalanced pipes get here later this week--but lots to do on the bike to get it on the road, per the resto/mods thread. I'm currently making DIY rear-set controls...

 

[Rudie]

View attachment 58196 Replace the nuts with stainless - heat cycles cause the plating to fall off plated nuts and studs then the bare steel nuts and studs rust together. Stainless nuts fitted with Copaslip or similar heat-resistant grease, you have a better chance of getting the nuts off the studs in the future.

 

[NM Bonny]

View attachment 58196 Replace the nuts with stainless - heat cycles cause the plating to fall off plated nuts and studs then the bare steel nuts and studs rust together. Stainless nuts fitted with Copaslip or similar heat-resistant grease, you have a better chance of getting the nuts off the studs in the future.

Great idea, thanks! Nice thing about these mufflers is if I keep the cans in good shape, I can periodically R&R the baffles to recondition/refinish them with high-temp engine paint.

 

[Bloodknot]

Okay, thanks.

I pulled the core from one of them and indeed the wrap is fairly thin (and tends to fall apart as you handle it), and not all the way down the core--though there isn't much room toward the front where they stopped wrapping. But as you can see, the size of the flange for the studs limits the thickness of material you can wrap around the core to considerably less than 1/2".

However, I think Acousta Fil and similar stuff is supposed to expand a little and isn't so delicate, so I still plan on putting in better material.

The perforated disc is smack in the middle of the core's length. But the holes in it are so small that as discussed much earlier in this thread, they seem to intend the gasses to be forced through or around the wrapping to some degree.

I'm still very tempted to try running them with no wrapping at some point, which would make them function like the vintage Sporty mufflers I'm using on my '51 FL. Those are a strictly metal baffle design--perforated core with disc midway down--but my reproductions (made by Gasbox) have a single large hole drilled in the originally solid baffle to flow more as needed for my 74" engine (and sound considerably louder).

Regardless, I measured the outlets: 1" on the OEM cans, and 7x.625" on the Dunstalls. So, the total area of the outlets are .7854" for OEM, and 2.1476" for the Dunstalls.

New unbalanced pipes get here later this week--but lots to do on the bike to get it on the road, per the resto/mods thread. I'm currently making DIY rear-set controls...

If it’s any comfort the two Ducati Performance carbon fibre sleeved cans on my Ducati work on exactly the same principle. A central perforated core wrapped in a few layers of fine stainless steel mesh. The void between this central core and the outer carbon fibre sleeve is then filled with wrapping.

The exhaust pulses punish the wrapping and when dissassembling the cans to repack them have found the first half depleted and very scorched allowing the heat to get to the carbon fibre which shows as a brown discolouration on the outside.

So the last time I needed to repack the cans I decided to protect the wrapping by not allowing any exhaust gas to reach it. The central core is a tad under 60mm diameter. I purchased a length of stainless steel tube that would just fit over the central core and profiled the ends to mate with the end caps of the cans which, on reassembly I sealed with silicone sealant.

End result, the packing now acts purely as thermal insulation preventing any further discolouration of the carbon fibre sleeve. They are floud but sound awesome. For our statutory annual vehicle test I refit the OE cans.

 

[NM Bonny]

If it’s any comfort the two Ducati Performance carbon fibre sleeved cans on my Ducati work on exactly the same principle. A central perforated core wrapped in a few layers of fine stainless steel mesh. The void between this central core and the outer carbon fibre sleeve is then filled with wrapping.

The exhaust pulses punish the wrapping and when dissassembling the cans to repack them have found the first half depleted and very scorched allowing the heat to get to the carbon fibre which shows as a brown discolouration on the outside.

So the last time I needed to repack the cans I decided to protect the wrapping by not allowing any exhaust gas to reach it. The central core is a tad under 60mm diameter. I purchased a length of stainless steel tube that would just fit over the central core and profiled the ends to mate with the end caps of the cans which, on reassembly I sealed with silicone sealant.

End result, the packing now acts purely as thermal insulation preventing any further discolouration of the carbon fibre sleeve. They are floud but sound awesome. For our statutory annual vehicle test I refit the OE cans.

Ah, so you basically turned them into straight pipes. Is there any kind of baffle midway along the core?

 

[Bloodknot]

Ah, so you basically turned them into straight pipes. Is there any kind of baffle midway along the core?

Nope.

 

[NM Bonny]

Nope.

Uh, yeah, I begin to sense what that machine sounds like as the revs climb...

Gorgeous bike, BTW. I'm glad I chose a fairing inspired by the '70s Ducati SS for my evolving OIF custom ride. Those Italians...

 

[NM Bonny]

Well, rats... I wish I had known about these mufflers, made by Conti, the Italian supplier for Ducati.

They are stainless steel, polished, and of straight-through design--I think. Perhaps Bloodknot, our resident Ducati expert, can correct me on this if I'm wrong...

At any rate, the standard length (Feked sells them in two lengths) is nearly identical to the Dunstall replicas, and the inlet is 1-5/8" or 42mm. Regardless, I'll run the Dunstalls for a while (I've ordered the Acousta-Fil packing), and should I wish for a slimmer, wide-open design when I fit a 750cc kit to the bike, might give them a try.

In the interim--or as an alternative--I can always experiment with baffles featuring different drillings: one big hole, as with my Gasbox vintage Sporty mufflers, but of varying sizes, or simply enlarged smaller holes like the existing baffle.

Can't wait to fire this thing up, though at my snail's pace it'll still be a while...

 

[Bloodknot]

Well, rats... I wish I had known about these mufflers, made by Conti, the Italian supplier for Ducati.

They are stainless steel, polished, and of straight-through design--I think. Perhaps Bloodknot, our resident Ducati expert, can correct me on this if I'm wrong...

At any rate, the standard length (Feked sells them in two lengths) is nearly identical to the Dunstall replicas, and the inlet is 1-5/8" or 42mm. Regardless, I'll run the Dunstalls for a while (I've ordered the Acousta-Fil packing), and should I wish for a slimmer, wide-open design when I fit a 750cc kit to the bike, might give them a try.

In the interim--or as an alternative--I can always experiment with baffles featuring different drillings: one big hole, as with my Gasbox vintage Sporty mufflers, but of varying sizes, or simply enlarged smaller holes like the existing baffle.

Can't wait to fire this thing up, though at my snail's pace it'll still be a while...

You are correct, the bevel drive SSs used Conti silencers. The ones you see on my machine are Ducati Performance and came with a replacement ECU as a freebie when I bought the bike new. Made in Germany by Remus.

 

[NM Bonny]

You are correct, the bevel drive SSs used Conti silencers. The ones you see on my machine are Ducati Performance and came with a replacement ECU as a freebie when I bought the bike new. Made in Germany by Remus.

Okay, thanks. It may be that it's just my eyes, but they look a bit slimmer at the megaphone end. But these Dunstall replicas will look grand, too... outstanding plating job those Chinese did.

I fiddled with the new cans today, and am happy to report that: (1) they fit with my DIY rear-sets (close but acceptable on the L/H side with the OEM brake lever mounting plate I fabricated); and (2) the OEM muffler mounts will work fine with either spacers, a gentle dog-leg bend, or both.

The last photo sums up my situation nicely...

Acousta-Fil en route from the UK.

 

[NM Bonny]

Here we go... a more formalized test fit to check the OEM mounts with the Dunstall replicas. They're close but no cigar: I want them long enough to grab both bolts (they only grab the forward one now), and they need a little jog to achieve the right angle.

The mufflers in these picks aren't as far in or canted upward to match the angle of the LF Harris unbalanced pipes' outlets yet. They clear my DIY rear-set brake lever just fine and look great.

Now, to make up some mounts and rewrap the cores with the Acousta-Fil that came in...

 

[sikatri]

Awesome! That is one beautiful ride!

 

[NM Bonny]

Awesome! That is one beautiful ride!

Thanks! It's s-l-o-w-l-y getting there. I'm eager to hear this baby run and compare the sound to the above clips posted a while back.

 

[NM Bonny]

I made up some mounts for these Dunstall replicas. Please see diagram with measurements, if folks want to recreate them, and also photos on the main restoration and mods thread for this bike, here.

 

[Lordmac]

Here we go... a more formalized test fit to check the OEM mounts with the Dunstall replicas. They're close but no cigar: I want them long enough to grab both bolts (they only grab the forward one now), and they need a little jog to achieve the right angle.

The mufflers in these picks aren't as far in or canted upward to match the angle of the LF Harris unbalanced pipes' outlets yet. They clear my DIY rear-set brake lever just fine and look great.

Now, to make up some mounts and rewrap the cores with the Acousta-Fil that came in...

Those look reeeel cool on yer bike! Yer bike is also looking reeeel cool. Have you tried those Hagons out yet? I love mine, even if they don't say Girling on 'em . . . ride real smooth and easy on the butt . . .

 

[Lordmac]

Here we go... a more formalized test fit to check the OEM mounts with the Dunstall replicas. They're close but no cigar: I want them long enough to grab both bolts (they only grab the forward one now), and they need a little jog to achieve the right angle.

The mufflers in these picks aren't as far in or canted upward to match the angle of the LF Harris unbalanced pipes' outlets yet. They clear my DIY rear-set brake lever just fine and look great.

Now, to make up some mounts and rewrap the cores with the Acousta-Fil that came in...

I just added that photo of your bike to my Triumph Photos Collection . . . for later perusal . . .

 

[NM Bonny]

Those look reeeel cool on yer bike! Yer bike is also looking reeeel cool. Have you tried those Hagons out yet? I love mine, even if they don't say Girling on 'em . . . ride real smooth and easy on the butt . . .

Hey, thanks very much. I am excited about how my vision for the bike is turning out. It has evolved a bit with the DIY rear-sets, DIY front disc conversion, and the fairing, obviously. But I think it's going to be a really nice-looking OIF Bonny.

No: I have yet to test-ride the bike, as per the main restoration/mods thread I'm just (finally) building the rear aluminum wheel after losing my fingerprints sanding and polishing the rear conical hub. Ouch...

But I'm very glad to hear you like your Hagons. Can't wait to try 'em out!

 

[NM Bonny]

Here is the final install. They look great, and I'm very happy with these Emgo replicas aesthetically. We'll see how they run with the unbalanced exhaust and shorty K&Ns.

There will be a period of silence on this thread until the thing's running, at which point I'll post a video of the exhaust note in the driveway and another on the two-lane blacktop leading down the canyon.

 

[NM Bonny]

Okay, finally got the last of the engine covers sanded, polished, and sealed up (primary chain case) with a new clutch installed, and fired her up. Seems to be a nice tight little engine.

My side stand needs repair, so it'll be a little while before I post the first riding video. But I'm going to repack these cans with the expanding fill I bought because... well, she's a bit loud with the awful packing that comes with these Dunstall replicas out of the box.

When I get the new packing installed, I'll post a video of how she sounds sitting in the garage idling and with a few revs, just to tide us over...