Exhaust Mid Box Help Please

[fastducs]

I'm sure this topic was discussed before, but search doesn't come up with anything relevant for some reason. So here is my question:

I have a 2000 cota 315r. What the heck is in that mid box? I am talking about the portion of exhaust that is between header pipe and silencer, i.e. what would normally be considered an expansion chamber. It weighs a ton! What is between the outer aluminum welded case and the perforated inner tube? Is it packing like in the silencer, and if so, then how do I repack it? Or is it just a huge amount of carbon buildup? Can the perforated innards be removed?

Edited December 30, 2006 by fastducs

[donmurray]

Probably oily carbon buildup. It's hard to remove and clean, so many of them may have never been cleaned. I tried soaking mine in a small tub of diesel with some fuel system cleaner added. Left it in there for a couple of days, but not much came loose. Next I suspended the expansion chamber vertically from a piece of pipe set across two saw horses, and set it afire. Just held a propane torch under it aimed at the bottom opening until smoke was pouring out. It would have a little flame inside and smoke would come out the top end. I would then turn off the torch and let'r smoke for a bit. When the smoking decresed, set the torch back to the bottom again. I did this from both ends until it would not smoke anymore. Tapped it some to get any loose stuff out. BTW, the diesel soak may have saturated the carbon buildup and helped the burnout procedure.

A little warning. If you let the flame inside get too big or burn too long, it may get too hot and melt some aluminum.

I think there's a type of cleaning dip that could be used. One that will not harm aluminum. Like those 5 gal buckets of carb cleaner. If you can find a radiator shop or such that has that type of cleaner it would be a lot less trouble.