Dunstall Ex 2-1-2

luckyed · Dec 1, 2018

Fitted the system on my '71 in the '70s (see avatar), and the '72 I picked up a year and a half ago came with the same Dunstall exhaust that some previous owner had put on way back when. Chrome was indeed kind of thin, but it cleaned up nicely on my current ride. Never had any trouble with the welds then or now. With attention paid to the mounting process, the system rides tight and rattle free, with ground clearance of the center pipe around 4.5-4.75 inches. As mentioned, no center stand, but I've gotten pretty fast at removing and replacing when I need to lift the bike. Currently running it with the stock 932 Amals w/stock jet settings and a K&N air filter (stock airbox removed). Don't know what's inside the silencers, but they seem fairly unrestricted. Nothing to compare it to, but it pulls hard all the way up to redline and sounds great. I also like how it looks with the low "Clubman" style bars and the Dunstall rear sets (thanks Madass!). As an additional note on design, the diameter of the header pipe increases after the first "Y" and then again after the second "Y" where it enters the silencers.

Reggie · Dec 1, 2018

oldmikew said:
when fitted with the original peashooters there was a noted loss of power...

To the best of my knowledge, the diameter of the rear "Y" piece where it fits onto the silencer was 1 5/8". Would it be possible to fit standard peashooters onto a 1 5/8" pipe?

Stephen Hill · Dec 1, 2018

Acotrel writes: "So you believe in experts ? Many university professors are simply lunch-time heroes."

I appreciate that we are a country mile off topic, but I can't resist responding. I get uncomfortable when people trash education, learning, science, and/or academics.
Interesting factoid: Hitler thought the academic freedom practiced by university professors was a threat to his control over the thoughts of the population, so he had them harrassed, gagged, and fired.

Back to Nortons.

Stephen Hill

Onder · Dec 1, 2018

...along with just about anyone else he could think of! :-(

If only his mum had let him get that BMW hillclimber he wanted....

oldmikew · Dec 1, 2018

Reggie said:
To the best of my knowledge, the diameter of the rear "Y" piece where it fits onto the silencer was 1 5/8". Would it be possible to fit standard peashooters onto a 1 5/8" pipe?

yes they slipped inside the rear y with the help of sleeves . Cannot remember whether I slotted the y but the actual joint was gas tight .. the only 2 on the whole system

baz · Dec 1, 2018

Reggie said:
To the best of my knowledge, the diameter of the rear "Y" piece where it fits onto the silencer was 1 5/8". Would it be possible to fit standard peashooters onto a 1 5/8" pipe?

Yep it was 1 5/8" I only ever ran mine with dunstle decibels

Snotzo · Dec 1, 2018

acotrel said:
So you believe in experts ? Many university professors are simply lunch-time heroes. .

Once again you excel yourself. If by your inference you are referring to Prof. Gordon Blair, quite obviously you have absolutey no idea who you are talking about.
I had the great pleasure of knowing Prof Blair personally for more than 45 years, and on numerous occasions visited the Queens University where he showed me all the latest research his students were busy with. Every bit of research was carried out with meticulous care and attention to detail. No room at all for suggestions, belief's, theories, suppositions, probabilities or any of the other fantasies you so easily indulge in, but solid research, the results of which were presented to those who financed the programs, and as these included over the years names such as Ford, Jaguar, Bentley, Yamaha, Bombadier amongst others, this should indicate what the worth of his research meant to these organisations.
How do you shape up by comparison ?

Fast Eddie · Dec 1, 2018

Stephen Hill said:
Acotrel writes: "So you believe in experts ? Many university professors are simply lunch-time heroes."

I appreciate that we are a country mile off topic, but I can't resist responding. I get uncomfortable when people trash education, learning, science, and/or academics.
Interesting factoid: Hitler thought the academic freedom practiced by university professors was a threat to his control over the thoughts of the population, so he had them harrassed, gagged, and fired.

Back to Nortons.

Stephen Hill

Quite right.

Experts can be wrong of course, but I’d sooner start out from a baseline given by an expert than one given by someone ranting away into keyboard who has clearly demonstrated that they do not know what they’re talking about.

Dutch · Dec 1, 2018

lcrken · Dec 1, 2018

eskasteve said:
Being older BITES!

But it's better than the alternative

Ken

jimbo · Dec 1, 2018

They did have non standard centerstands.

Reggie · Dec 2, 2018

oldmikew said:
yes they slipped inside the rear y with the help of sleeves .

I actually thought of this possibility after posting last night.

But the original poster was asking whether or not the Dunstall 2-1-2 system worked well. I'm sure you're likely to be correct about the reduced power after fitting standard 1 3/8" peashooters to the 2-1-2 downpipes, so that is not a good idea if you're hoping for more power, but by so doing you are corrupting the design of the system by reducing the incremental increase in the pipe bore which I would think is likely to be there for a reason.

acotrel · Dec 2, 2018

Probably any exhaust system which is really effective in producing high power, will be too loud to be legal. That might be the reason that Exup was developed for MotoGP bikes. It allows more radical cam timing to be used.

bill · Dec 2, 2018

the exup has NOTHING to do with noise. also it has been around before moto gp

acotrel · Dec 2, 2018

Snotzo said:
Once again you excel yourself. If by your inference you are referring to Prof. Gordon Blair, quite obviously you have absolutey no idea who you are talking about.
I had the great pleasure of knowing Prof Blair personally for more than 45 years, and on numerous occasions visited the Queens University where he showed me all the latest research his students were busy with. Every bit of research was carried out with meticulous care and attention to detail. No room at all for suggestions, belief's, theories, suppositions, probabilities or any of the other fantasies you so easily indulge in, but solid research, the results of which were presented to those who financed the programs, and as these included over the years names such as Ford, Jaguar, Bentley, Yamaha, Bombadier amongst others, this should indicate what the worth of his research meant to these organisations.
How do you shape up by comparison ?

We have a refugee here in Australia who used to work with Blair at QUB. In fact he was the guy who started historic racing in Australia. If there was ever any way of getting something wrong, he would find it - not Blair, but his idiot disciple.

oldmikew · Dec 2, 2018

Reggie said:
I actually thought of this possibility after posting last night.
But the original poster was asking whether or not the Dunstall 2-1-2 system worked well. I'm sure you're likely to be correct about the reduced power after fitting standard 1 3/8" peashooters to the 2-1-2 downpipes, so that is not a good idea if you're hoping for more power, but by so doing you are corrupting the design of the system by reducing the incremental increase in the pipe bore which I would think is likely to be there for a reason.

as i found out ... my issue was the build quality ,if the original system had sealed and not produced endless bags knocks and rattles , then it would have stayed on the bike .It was thrown in the dustbin before it had chance to rust. Certainly it produced the claimed mid range 5bhp which is a lot . I have since noticed that Dunstall stuff in general is much better thought of in the US than it is here... I would have thought that back pressure and over all length would be crucial factors. A reduction in pipe id can lead to performance increase , but it certainly did not in this case.
Clearly Dr Blair knew what he was doing which was why I posted though this issues has nowbeen well and truly aired

Brithit · Dec 2, 2018

I'm currently running one on my '72 Combat. No cracks I've spotted yet, but I know they have a reputation for that. I'm using the Emgo Dunstall look alikes, with the fiberglass packing removed. The sound is different, but I like it. Side by side comparisons with another Combat with pea shooters is interesting, but they both sound good to me. Power difference - absolutely no idea. I would mention that the Dunstall centerstand needed a little extra metal on the bottom for my tastes. With stock wheel sizes, suspension, etc., it was more like a ride-off stand with both tires touching the ground. Made me a little nervous on anything other than a perfectly level parking spot. I didn't want to weld anything on to it, since it was unmolested, so we designed some small plates to bolt on to the flat part of the stand. Worked a treat.

bill · Dec 2, 2018

not from the circle i know. it is more refered to as junkstall. yes in my experience the exhaust did as claimed with more mid range but it was a poor execution as with about all his junk.

oldmikew said:
I have since noticed that Dunstall stuff in general is much better thought of in the US than it is here...

bill · Dec 2, 2018

don
you might want to add a loop of safety wire under the center pipe at the front cross member as a safety catch as the center can fall off of the 2 head pipes.

Brithit · Dec 2, 2018

bill said:
don
you might want to add a loop of safety wire under the center pipe at the front cross member as a safety catch as the center can fall off of the 2 head pipes.

Good idea!

Dunstall Ex 2-1-2

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