Proof that dunstall stuff can last
- Thread starter baz
- Start date
Fast Eddie
VIP MEMBER
- Joined
- Oct 4, 2013
- Messages
- 22,682
45 years of use… or sitting on the shelf ?
baz
VIP MEMBER
- Joined
- May 26, 2010
- Messages
- 8,531
ashman
VIP MEMBER
- Joined
- Jul 11, 2010
- Messages
- 6,449
My header pipes were made by a good muffler shop back in 82 by a very talent exhaust bender on an old mandle bender all by eye 15 minute for each header, was when I was converting my 850 to the Featherbed frame and they are still on the bike after all this time and still ridden, they are showing their age and I have brazed up 2 very thin holes right on the first bend of the left header, but that was over 20 years ago when that was done, he was a old biker and only charged me $20 and next door was a new chrome shop that opened that week and he charged my $20 to chrome them.
The muffle shop is still owned by the original owners but my fitter passed away many years ago and the old mandle bender been long gone as well the chrome shop was gone after a few short years, in 83 I also got the same fitter to bend up a set of SS headers for my 81 Triumph Thunderbird, he charged me $40 to bend up, my Norton headers would have over 140k miles on them.
Pics of both bikes with the headers made by Ken Toy at Toy Mufflers at Redcliffe, I have a love of upswept pipes and the both Norton and Triumph headers were bent to tuck right in, was lovely watching him bend them up and making them to fit.
The muffle shop is still owned by the original owners but my fitter passed away many years ago and the old mandle bender been long gone as well the chrome shop was gone after a few short years, in 83 I also got the same fitter to bend up a set of SS headers for my 81 Triumph Thunderbird, he charged me $40 to bend up, my Norton headers would have over 140k miles on them.
Pics of both bikes with the headers made by Ken Toy at Toy Mufflers at Redcliffe, I have a love of upswept pipes and the both Norton and Triumph headers were bent to tuck right in, was lovely watching him bend them up and making them to fit.
baz
VIP MEMBER
- Joined
- May 26, 2010
- Messages
- 8,531
Just made these in stainless using welding elbows for my girlfriends yam
Attachments
Schwany
VIP MEMBER
- Joined
- Apr 22, 2020
- Messages
- 3,650
baz
VIP MEMBER
- Joined
- May 26, 2010
- Messages
- 8,531
No there's no sleeves used
The joins are prepped and tig welded
I'd rather have bent the tubes but I don't have access to a mandrel tube bending machine anymore
Schwany
VIP MEMBER
- Joined
- Apr 22, 2020
- Messages
- 3,650
Hey I don't think the engine will care that you welded it up and didn't use a bender.
Tig looks like it is a tactile doable welding technique. I'm still hesitant to even try welding. I have a brand new Arc stick welder my next door neighbor gave me when he moved. Cheap little inverter thing. I don't want to spend a day sticking sticks to metal and tripping breakers. Working in the air above the joint is really a foreign feel too.
Anyway well done. I am envious of that skill.
SteveBorland
VIP MEMBER
- Joined
- Nov 15, 2010
- Messages
- 977
Try using gas to weld exhausts
Then you think tigging is easy...I learned the art making up exhausts for engines on the dyno stand at the Toyoya factory where I was doing the practical part of my engineering studies.
baz
VIP MEMBER
- Joined
- May 26, 2010
- Messages
- 8,531
I've got 49 years as a fabrication welder behind me and have made many many exhaust systems
I usually use a stick welder to weld these up
- Joined
- Jun 30, 2012
- Messages
- 14,890
One of the things I have learned is that any restriction at the outlet of the collector of a 2 into 1 exhaust, can cut more than 2000 RPM off the top of the usable rev range of the motor. I had not seen a photo of the Dunstall pipe until recent years. It is a very good answer to the noise problem without killing performance. The Laverda 750 SFC is a 180 degree motor, and the problem is solved by the cross in the exhaust system, under the gearbox. With my bike the tail pipe of the exhaust has the same cross-sectional area as the sum of the header pipes, and it is the same length as a header pipe. With exhausts, we are dealing with resonance which affects cylinder filling. My system works well, but it is too loud.
Many people have probably never tried to gain performance by modifying their exhaust system. It is a learning experience. When you build a race bike it cannot ever work perfectly the first time you ride it. Most theories are bullshit. When you are a beginner, you do not know what you are feeling when you ride a motorcycle. The motorcycle shapes your brain. Mike Hailwood's father bought him a championship-winning Mondial 250, to learn on. My brain was shaped by garbage.
Many people have probably never tried to gain performance by modifying their exhaust system. It is a learning experience. When you build a race bike it cannot ever work perfectly the first time you ride it. Most theories are bullshit. When you are a beginner, you do not know what you are feeling when you ride a motorcycle. The motorcycle shapes your brain. Mike Hailwood's father bought him a championship-winning Mondial 250, to learn on. My brain was shaped by garbage.
- Joined
- Jan 7, 2023
- Messages
- 231
I can't see any logical reason that the collector should be twice the cross-sectional area of one primary. The primaries are using the collector mostly separately since it's a 360 degree twin. To optimize extraction, I would expect the secondary should be somewhere around 1.4 X a primary cross-section. The length of the secondary would affect the RPM range where extraction peaks; there wouldn't be anything magical about it equaling the primary length. Shorter would make more sense to come closer to the same volume as a primary clearing the way just in time for the opposite cylinder's charge to enter.
baz
VIP MEMBER
- Joined
- May 26, 2010
- Messages
- 8,531
A polyromy tube polisher makes life easyLooks very smooth (on the outside!)
Those pipes are not finished to any real standard
I could go up on the belt grits to give a satin finish and then onto a mirror finish
But that's not what this bike is about
It's basically lacquered bare metal
