It also looks like the pipe is welded right at the break. In most Harley applications there are no welds at the flanges. Believe me when I say my Harley shakes at idle and the exhaust is mounted on sliding rubber mounts at the rear of the bike. My mufflers can move as much as 5mm to 6mm lengthwise to the bike. This puts lots of stress on the flanges.

I've seen videos of the M3W motor vibrating on idle and it's no where as much as the rubber mounted Harley touring bikes have.

But with the necked down tip of the header pipe welded to the larger pipe, that has to be a weak point. Just as the pipes are breaking at the welds on some of the Brookland pipes leading into the mufflers.

I've made up a few V-twin header pipes from scratch using "J" and "U" bends with straight pipe. I've also modified several car header systems. I've used both MIG and TIG welding techniques and other than looks, both seem to have held up well.

I would never use anything less than 16 gauge tubing. All of my pipes have been mild carbon steel, not stainless. 16 gauge is 1.6mm wall thickness. At this thickness I've never had a pipe break at a weld or break period.

The M3W is unique in that the length of the header pipes is quite long and the flex couplings are not all that flexible. This length does put an unusual amount of stress at the head flanges.

Dan