Muffler Chopping Adventures

[kjaj97]

Wanting the improved performance and throatier sound of performance mufflers, but not able to justify the $700-$900 expense, I bought a used pair of mufflers and started to chop. Actually, I spent an hour trying to get the aluminum covers off the stock mufflers (probably the hardest part of the job) and then chopped.

 

I thought about drilling holes in the back wall of the muffler as others have done, but after looking at various pictures (FAQ exhaust thread – thank you al roethlisberger and contributors) I thought modifying the internals might work better.

 

My first attempt (which I hope I can illustrate with a picture below) involved cutting the muffler in half near the middle. The stock muffler is a semi standard design. Exhaust flows into a chamber through a pipe "A", backwards through two pipes"B" into another chamber, and then out through a heavily muffled pipe"C".

 

I removed a section of pipe C (you can see how deep C is in the picture – it was flush with the main cut originally) so the exhaust gas could flow directly from A to C with no back flow. I got the pipes welded back to together at a muffler shop ($40 – a difficult weld due to the thin material) and got ready for aural bliss and high performance.

 

It didn’t work. The exhaust sound was similar to stock with a somewhat annoying back rap on deceleration. I read somewhere that a guy actually designed a performance exhaust system with smaller diameter pipe to get that 50’s sounding back rap. Pipe C is small diameter and heavily muffled so that is what I got.

 

I was ready to trash the whole thing, but then I got another idea – next post

[kjaj97]

Since Pipe C was my problem, I decided to take the blunt approach - I cut it out. Three cuts were required:

 

1. Cut the muffler in half just in front of the rear spot welds.

2. Cut the welded rear end cap off behind the weld so the cap can be welded back on.

3. Cut the angled pipe extending out of the cap just ahead of the radius. This is a little tricky and required the use of a cut off wheel as well as the chop saw.

 

By the way – a chop saw makes these cuts pretty easy and fast. Other tools might be more difficult to keep square or slower

 

Then I dumped the rear section of the muffler, had the end cap welded back on to the now shorter cans (easier weld - only $20) cut the aluminum cover to the right length, installed the cover, and bolted the “bolt-on” end caps on.

 

Now the exhaust flows out pipe A and out of the end cap. It has a slight mechanically baffled sound (sort of similar to a Flowmaster) but I like it. One could even tune the exhaust sound by modifying the opening of the bolt on end caps. I ran the bike without the bolt on end caps and it was a little loud, so I left the opening stock. I suppose I could modify one set of end caps and then use the stock ones if I wanted a quieter exhaust.

 

I have not decided whether to leave cans silver, paint them black or polish them to give them that fake Staintune look.

[Enzo]

A man after my own heart. God bless him.