Dunstall 2-1-2 info required.

I've decided to go ahead and get a bespoke Dunstall 2-1-2 built for my Commando, and RennieK has previously written

One characteristic Dunstall (Dr. Blair) used for 2 into 1 into 2 was to step up the size of the tubing at every joint so the end tubes were 1/4" wider than the headers.

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So if the pipes started at 1" 3/8" at the head, and were 1/4" wider by the time the pipes split underneath the gearbox, was there just one increase in size (at one of the joints front or back) or two increases in size i.e. at both "Y" connectors? I'm trying to get this information correct before I commision the building of. I see that Duntall silencers are avilable in 1" 5/8" inlet diameter which would equate to 1 X 1/4" increase, or 2 X 1/8" increase.

Any help is greatly appreciated.

My set is apart right now, what measurements do you need?

openroad wrote;

My set is apart right now, what measurements do you need?

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openroad, thanks for the offer.

If you could, I would like the measurements of;

1. The outside diameter of the pipes just before they go into the first "Y" connector.
2. The outside pipe diameter of the single pipe that leaves the "Y" at the first junction.
3. The outside pipe diameter just before the single pipe splits back into 2.
3. The outside diameter of the pipes after it has split back into 2 just before it goes into the muffler/silencer.

Hope this isn't too much measuring.

OK, I'm headed out to the shop, back soon.

Reggie said:

openroad wrote;

My set is apart right now, what measurements do you need?

Click to expand...

Click to expand...

openroad, thanks for the offer.

If you could, I would like the measurements of;

1. The outside diameter of the pipes just before they go into the first "Y" connector.
1.39"
2. The outside pipe diameter of the single pipe that leaves the "Y" at the first junction.
1.52"
3. The outside pipe diameter just before the single pipe splits back into 2.
1.52" slides into 1.63" approx.


3. The outside diameter of the pipes after it has split back into 2 just before it goes into the muffler/silencer.
1.63"




The header pipes seem to be aprrox. 1.39, the center section seems like it's all about 1.5, rear section all about 1.63. Center section takes a beating from install and curbs and other stuff, but I think the measurement is close.

openroad......what can I say!!! and with pictures too 8)

I really appreciate that.
Your measurements equate to 1" 3/8" down pipes,
After the Y connection, the single pipe 1" 1/2"
Onto/into the silencers, 1" 5/8"

So as RennieK said, "a step up at every joint." You have just confirmed it.

Thanks again. I'll check I can get it done to these specs and then order.

Good Luck, you'll miss your center stand at times, but they sound really good with the Dunstall mufflers, and you won't be seeing many others with your set-up. Takes a different hanging system for the mufflers, too.