Broken down-pipe.

Whilst out blasting up the A1 today I noticed popping on over-run followed over the next 15 to 20 miles in the down- pipe on the left hand side completely breaking off where the insert is welded ? on.

I assume that this is because of some stress on the header when the pipes were fitted, but these pipes have only done about 2000 miles over 2 years, so a bit disappointing.

Any offers of why. Am I a sh*te mechanic or does this happen occasionally?

Same thing happened to a Motad Neta 4 into 1 on my Kawa 1100. Twice. Replaced by Motad even out of warranty. Stainless seemed a bit thin, and the nature of fitting kept some stress on the pipe at the exhaust flange. Maybe yours has the same problem?

Are we saying that it’s thicker where it goes into the head and this has snapped through the middle of the weld which joins thick to thin?
If so and it’s a butt joint not a overlap fillet weld the problem is lack of fusion in the butt weld.
This could possibly be a orbital weld where the machine has not been set up square leaving only the edge of the cap holding this together if you can get the other one radiographed and it’s in the same state I would be looking for a refund. Happy to radiograph it for you foc if your local?

What make exhaust are we talking about? I’ve never had a stainless steel system fail, ditto standard downpipes

not sure if you have loosened the bottom off in the photo or not If not the downpipe was under a lot of tension i alway loose assemble keep nipping topand bottom clamps while tapping with rubber mallet to get them to line up

If it was under tension over a fair length ie head to collector box thin stainless would just bend.
When you magnify the photo it looks like it’s sheared off through the centre of the weld.
A weld that I feel has no penetration ie it is simply laying over the top and sealing the pipe.
if the two bits of pipe had been tapered and welded with some penetration this would not have happened. (Not the fault of the person who fitted it)

Same here. (The SS version is by Armours of Bournemouth)

OK, I’ve had a closer look tonight.
I’m not a fabricator or welder, but the part that fits into the head is one piece of metal with a shoulder, and you can see the brazing where the pipe is then attached, over the shoulder and onto the stub and this is where the failure has occurred.

The pipes are 40mm o/d from a well known supplier of Guzzi parts and are mild steel (not stainless). I have checked tonight and I have had these for 2.5 years although they didn’t get used for at least 5 months or so from the date of purchase.

I’ll probably email the supplier on Friday with the pictures and see what they have to say.

The pipes were still fitted when photographed, but they have a push in collar on the front crossover which had detached itself due to the fracture of the pipe as had the rear crossover pipe and so had move from the position that they would have been in pre-braze failure.

Colincs, hanks for the offer of an x-ray, hopefully wont be required but I live in Leeds fyi.ReggieV2014-09-03 21:43:54

I am over near hull so if it would help your case no problem. If we prove the other pipe joint is of poor quality and will fail soon it will strengthen your case…

I had a chromed steel downpipe on my S3 snap in the same place a few years back, but it had done more mileage than yours. I put it down to age and bought another, but like Ray says, it’s a good idea to try and assemble the system so that there is as little tension as possible, I always copperease where the H sections and other parts slot into each other. TBH I don’t think these parts are exactly produced to a very high standard, and as Colincs says looks like the original weld was weak.

    That's a new one me ... never seen that before, or a double-skinned one like that ..     I thought at first you meant the flange had come off, which I would've thought was more likely.
Yes I asemble it all loosely from front to back, then tighten the head clamp nuts first, H-crossover 2nd, silencers last.

Actually no I don’t, I get the downpipes and H-section sorted out and screwed down first, then put the silencers on.

Over the years both sides of my Armours SS downpipes have come adrift at the welded flange.Left side when the system was ten years old, right when it was 20 years old. On both occasions I sent the pipe back to Armours and had them rewelded free under thier lifetime guarrantee! I can’t speak too highly of this firm, repolished before they were sent back as well.

I’ve had this happen to an SS down pipe.Mate at work welded it up.Long time ago so cannot remember whose downpipe it was.