Chemical muffler decarbonizing

[n0yyw]

So I've been reading a lot and tinkering on my 86 Spree. I did as much as I could to improve my Spree and it's running well but I think I've got carbon buildup in the exhaust. I don't weld so cutting it open is out of the question. The flame-out procedure seemed a little out of my grasp as well. So I went with a chemical procedure. Sorry if this has already been posted on here. I couldn't find any references to it with the search, and precious little reference elsewhere online to the concept.

Sodium Hydroxide (lye / caustic soda-lye / NaOH) attacks carbon. I was surprised how hard it was to find genuine lye. You used to be able to buy it in grocery stores in the cleaning aisle. I got a gallon of liquid drain cleaner that was comprised of Sodium Hydroxide and Potassium Hydroxide.

Do *not* use Draino Gel or any dry powdered drain cleaner! The powdered stuff usually contains aluminum chips that react violently when water is introduced in order to generate heat. Get pure Hydroxides if you can. Sodium Hypochlorite is present in some cleaning agents along with the hydroxide. That's just bleach and dilutes the effectiveness but shouldn't harm anything.

Okay then... if you do this, wear gloves and a *full*face*mask*. Please! Lye is used to dissolve bodies in graves to hide the evidence. It will burn your skin quickly. Don't let it contact aluminum either as it reacts violently. Please be careful.

I filled a tall, narrow plastic trashcan with a couple of bricks as filler (sideways) and added the gallon of hydroxide solution. I followed that with two gallons of hot water. Then I submerged the muffler, tailpipe first, so that it was under the solution up to the pipe portion (which I had already brushed out pretty well). I gently tilted this around a bit to get the solution to fill any air pockets and let it sit for a while.

Every thirty minutes I pulled out the muffler and let the lye drain from the tailpipe. It was black like ink with all the loose carbon! I repeated this over the course of about 4 hours. It's a slow chemical reaction - be patient.

Finally it's time to clean it out. Keep the gloves and mask on! I used a garden hose and ran water in forward through the entire exhaust, then backwards through the tailpipe, etc. Just flush the heck out of it. I spent nearly an hour cleaning the thing. Be diligent here and don't leave any lye behind. You won't believe the amount of powdered carbon gunk that comes out!

Finally, to help dry it quickly, I used a propane torch to heat it up moderately. Not glowing red or anything like that - just warm... meanwhile, dump the lye down the toilet! It's drain cleaner, after all! Flush many times...

I wish I had done a before/after weight test. I wasn't thinking about it at the time.

Comments? Suggested alternatives? I'm going to do this to my Yamaha Razz next. It has a muffler which has glass in it and can't be burned clean so chemical cleaning is the only method possible.

-- Tom in MO