Exhaust flange repair/ rust removal (79 KZ650SR)

Hey all, I’m new to the forum as I recently picked up a ‘79 KZ650SR as a project. After taking off the exhaust, I noticed that on the header for cyl. 1 and 2 that the mating surface is cracked and has a chunk missing .

So, I thought of a few different ways to fix this so there’s no exhaust leak, but wanted to get some other ideas.

My first thought was taking some JB Weld putty (extreme heat version) and trying to fill it in and then grind it back to the profile so it seals.
Second thought was TIG welding some material and then shaping it...provided the stock exhaust is stainless?
I then noticed there seems to be an inner fitting or something pressed inside the exhaust so maybe I could remove it and make a new one?
Or perhaps just modifying or replacing the copper washer to make it seal would work?

I won’t be able to fit the exhaust back on till I turn out some stainless steel studs for it on the lathe next week (we will see how that goes). Anyways, any other ideas or thoughts on what would work best? I would just go buy a nice Kerker or something but that’s a bit out of budget. Also as you can probably see, the ol pipes have got some surface rust, any cleaning tips besides Scotch Brite and elbow grease?

The stock exhaust is not stainless. Also, the stock exhaust is dual pipe (a pipe inside a pipe) which helped prevent the chrome on the outer pipe from turning blue. Ed

I had the same issue on my V/H header. I used my small welder to lay a bead filling the void and used my grinder to reshape it. It's been holding for two years now. The shells bend at the flange so they won't fit evenly and that's what I think caused it. I straightened them with my vise.
Steve

The stock headers are double wall to keep the chrome from blueing. easiest way to repair would be to lay down a small weld bead and file it back. since you have access to a lathe you could turn some rings and weld those on as well.

Well I guess I wasn’t aware of double walled exhaust systems so that’s good to know.

It looks like I will probably try the welding route, and I did notice after I sandblasted the shells that the edges weren’t straight so I will see what I can do there. Thanks for the helpful video SWest.

Also here’s the studs I made, after a few unsuccessful tries with a die I attempted single point threading for the first time and it went decently.

You did a good Job on your self made studs.

I change most of my nuts and bolts to stainless steel shells, studs,nuts and bolts.

Thanks Scirocco, and also that’s a beautiful bike!

I would also replace everything with stainless, but since its so expensive I usually don’t until a bolt is stripped or something is bad enough to warrant replacing.

Scirocco wrote: I change most of my nuts and bolts to stainless steel shells, studs,nuts and bolts.

I've used stainless fasteners where they attach steel pieces, but I have not used stainless fasteners where they attach to aluminum. My understanding is that doing that can result in galvanic corrosion. (See link below.) Have you found that to be an issue where stainless and aluminum are bolted together? Thanks, Ed

www.albanycountyfasteners.com/blog/2017/...-steel-and-aluminum/

Almost all the bolts on engine/trans have been replaced with SS SHCS on my 650 for years, from the beginning I used Never Seize on the threads and body, unless the application dictated Loctite and have not had any trouble with galvanic activity. Dry I believe would be a issue.....

Ive had many bikes where i replaced the bolts with stainless and never had a problem. However it is critical to use anti-sieze with a stainless nut on a stainless stud. Its quite easy for them to gall and seize.