Topic: Quiet this son of a gun down!

[eigenvector]

Riding around today on the Nighthawk, something I noticed (as did everyone within 2 blocks) is how LOUD!!!! it is when the main jets kick in.  <rrrrrrrrrrrrRRRRRRRRRRRR>

The previous owner of the exhaust system (the originals were rusted out Yoshis) took a torch to the mufflers and gutted them totally.
I tried to recreate the original exhaust from pictures online, but since the internal baffles were removed I had little in the way of options.

So I have an open trumpet shell exhaust - my goal is to fit something in there that will effectively quiet the sound.  It doesn't have to be silent, it doesn't even have to be legal - but it does have to be tolerable by people within 2 blocks.
http://i.ebayimg.com/images/g/UjUAAMXQ0pNRulaz/s-l300.jpg

That's an example of the exhaust system.  I still have the end-plates for the mufflers - so I only need to fit something to them, but if I have to I can completely replace them with something else.

[Terry in Australia]

Here you go Rob, buy some of these things, (just do an ebay search for "Motorcycle exhaust Baffle") and some fibreglass exhaust wrap, shove it up your............ er, megaphone, screw or rivet it in place, and enjoy your magic carpet ride......... I've done it, and it works perfectly.

[eigenvector]

I'm an engineer - so I can't just let it go at that.

I have some perforated sheet coming in the mail, I'll make the exit pipe from that - wrap it in baffle material (have some already on hand) then see if that helps out.

I am just not a fan of loud bikes - this one is LOUD!

[Terry in Australia]

No worries, I work with Aerospace engineers so I know how they like to turn a simple solution into a major engineering feat for the same result (if they're lucky) so I'll be interested in seeing pics of your solution! Cheers, Terry.

[eigenvector]

We'll see - this is iteration 2.  First I have to get the material.

[jag767]

I'm an engineer - so I can't just let it go at that.

I have some perforated sheet coming in the mail, I'll make the exit pipe from that - wrap it in baffle material (have some already on hand) then see if that helps out.

I am just not a fan of loud bikes - this one is LOUD!

I just picked up a ducati m750 that is like that. With straight pipes, it's so unnerving that riding it home I pulled the clutch in if I even thought I saw a cop! When the guy selling it to me started it I actually jumped not expecting that amount of noise.

[Terry in Australia]

Loud pipes save lives! (if not eardrums, and relationships with neighbors........ )

[Don R]

 I enjoyed making the baffles for the 76F mufflers. Let your imagination be your guide.

[eigenvector]

Well....

I think I made it louder   

7" of 1/8" perforated aluminum plate wrapped in coarse stainless steel wool.  It's better than what was there originally - nothing.

Trouble is I only have 7" to work with - there's a diffuser plate welded into the muffler can 8" into the body.  With only 7" to work with there isn't a lot of room for the exhaust air to expand and diffuse within the muffler.

If this fails - I'll try a design that forces the exhaust to change directions before exiting.

[Terry in Australia]

7 inches is always enough mate! But seriously, depending on the OD of your muffler, 7 inches of baffling should be fine, I had to do it on my CX500 Custom when I installed some excellent looking (but pretty much unbaffled) stainless steel megaphones and I don't reckon I had 7 inches of space to fill with quality fibreglass baffle material (even stainless steel wool isn't great, it's not packed tight enough) and I ended up with a nice mellow sound that passed a roadworthy certificate inspection. Cheers, Terry.

[eigenvector]

Okay, so I took it out today after work and it's better.

Sounds as loud as any aftermarket sport bike pipes, the high-end sound is quieter, but the low end sound is a bit higher.  All in all it evened out the volume.

I'll stop farting around with the pipes for now - this bike won't get out enough to bother the neighbors.  It still needs a lot of TLC.