So, I’m going to loose the ornamental outer exhaust header shell.   Has anyone separated it from the exhaust core?   I’m thinking to cut it off with an angle grinder, leaving some external tube tabs at the top end to bend down to the core, TIG together.   Why?  I wanna loose the weight, use the space, and rout the exhaust into a relatively cramped bend around a sidecar strut.

I’ve read several reports of the inner exhaust tube inside diameter- 1.3”, and 1.27” -but don’t have a caliper to throw on the part, take a measurement.  Regard the 2 attached images.   The first is the header top end.  Notice a couple things- the opening is smaller than the inner pipe diameter, and there is a hump on the bottom of the opening, constricting it further.   The second image is the other end of the exhaust pipe; a few things of interest here- between the inner and outer pipe is a split spacer, and opposing faces of the inner tube have been flattened.   Measuring across the undeformed axis, I find 34 mm, or about 1.34”.   I reckon metric pipe, coming from Japan- so, here in the States, what would be a close equivalent?