Soooo..... I'm working on my GTR "runner" and the mufflers are in just average shape but very useable for a daily driver sort of bike and they are 10 footers... they look fine 10 feet away. But they have a few issues.
First, one of them has almost the rear third of the bottom seam blown apart, like there was an explosion at one time in the past. Maybe the muffler filled up with unburnt gas due to a dead cylinder when all of the sudden it fired and lit it off, who knows. The other muffler has a brown ring or discoloration about 2/3 of the way down which Carl (I think) said may have been due to that cylinder running too lean. That muffler also has a small hole on the bottom.
I decided to have the split and the hole welded up but my cranky drunken welder guy wouldn't do it until I cleaned the oil and left over gas out, so I pulled the baffles out. One baffle came right out but the other would move maybe 1/2 inch and wouldn't budge. I hooked a slide hammer up to it and hammered it out. Inside the muffler there are round bulkheads that form chambers, and the last one on that muffler had broken its spot weld and was sitting in there sideways. This was binding the baffle as I was trying to pull it out.
As you can imagine the baffle was no longer quite right, and I was comparing the two for damage. As I was looking at it I noticed that inside the baffle there were plugs placed at strategic locations to force exhaust gas in and out of the baffle holes. BUT... on the one side with the discolored ring the very first plug had broken its spotwelds and had slipped down and jammed in a spot that would have for all intents and purposes plugged the muffler, because it was right where one of the bulkheads was at. So the exhaust gas couldn't get past the baffle plug or the bulkhead. Guess what? That is right where the discoloration is at. I wonder....
Anyway, I pulled a baffle out of my rusty parts bike, and after the welding was done I put that in there. All the welding was at the bottom of the mufflers so unless you crawl under there you can't see it. When I get this back together maybe it will run a little better because the one muffler won't be plugged up. It really didn't run too bad before.
So I gots me some fairly decent useable mufflers. They will work just fine, and hopefully I'll get some expansion chambers from Kotaro someday.
I also have a care package from Richard on it's way so things are moving in the right direction!!
