Topic: Drilling out baffles?

[DammitDan]

Anyone tried this before? I don't want my '82 CB650 4-into-2 to be annoyingly loud, but on the other hand it just seems too quiet right now (especially at idle... I've got it down to idling at 1050 when it's warm, and boy it would sound good if only the engine didn't drown out the exhaust!)

Any advice would be appreciated. Seeing as how I don't even know what the baffle looks like inside the muffler, I don't know how deep/how many holes I would need to drill to make it sound decent.

[Killer Canary]

Are your baffles removable? Stock?

[DammitDan]

Stock everything.

[Jim Shea]

I have the same question with a Motad(4 into 1) exhaust?

[Jim Shea]

I called Motad here in the UK and asked the question about drilling. The only bit that is accessible is the final baffle plate in a Motad, they said if you drill it out it will increase the noise very slightly and reduce back pressure and increase performance!!
I tried it and put 2 holes in the plate and it has made a tiny difference to the noise, but not much?
I suppose the bigger the hole the better, but would that effect the carbs?

[Killer Canary]

My wife's 550F has a no-name megaphone installed by PO which let out no more than a whisper and was basically strangling highway performance but, surprisingly for a cheapo, had a removeable baffle which I tossed and replaced with a home-made free-flow baffle.
The difference in performance and sound is profound and cost under $10 to accomplish.

[Buffo]

it depends on how much you drill...if it will affect jetting...

drill and chop...drill and chop

Buffo The Magnificent

[Jim Shea]

What will the immediate symptons be if you have drilled too much and affected the jetting?

[OldBoy]

I fitted a Motad exhaust to my rebuilt CB500 years ago and didn’t realise how restrictive these exhausts are until it rusted out.
I think Motad use the same silencer unit for all bike from 250cc upwards, probable OK for a 250cc bike but too restrictive for a 500cc plus bike.
There is a baffle close to the end of the silencer which I put a ½ inch hole in soon after getting the bike on the road.
Didn’t notice any real difference, noise or performance.   
What you need is a bar of some sort to reach to the inlet end of the silencer to get a hole in the other baffles, two more if I remember correct.
The hole size would need to be large to make any good improvement and you will still have a quiet silencer.
From the plug readings I have taken it seems that this bike is not very sensitive to exhaust changes, perhaps due to the low state of engine tune.

[Jim Shea]

I have drilled 6 x 8-9mm holes in the end baffle plate and it has made a tiny difference to the noise. Someone did tell me that you need to get a bar with a pointed end on it and push a hole in the end of the baffle. Question is, how do you know when it has reached the baffle that you want to make a hole in?
Jim.

[Jim Shea]

The plate drilled is about 3-4 inches from the end of the silencer. I don't think this is actually a baffle though? or is it?

[Jim Shea]

I just measured and you can get a thin rod approx 11 inches in to the silencer before it meets resistance; would this be the baffles it is hitting?
Jim.

[OldBoy]

Yes, I recon that’s the next baffle.
The silencer is sectioned off  with these baffles, each baffle has two lengths of  small bore tubing welded in connecting each section.
Had the old silencer in the shed after cutting it open to see how it was made but finally threw it out, otherwise I could have posted a photo.     

[Jim Shea]

I managed to test the bike today and it sounds better, with no apparent detriment to performance. The bike sounds almost the same up to 4k, then it has a nice raspy note, which I like. Do I stop now or go for a hole in the next baffle? What do you think?
Jim.

[SteveD CB500F]

Jesus Frank.

There I was reading Jim's latest words and your avatar winked at me!!

Spooky...

[Jim Shea]

The same thing happened to me and I thought I was going mad and seeing things!!

[Bob Wessner]

At first, I was going to ask what are you guys smoking?! Then, by God, it winked, ha!

[Jim Shea]

Creepy isn't it? but you find yourself staring at it.

[OldBoy]

The ideas behind my avatar; I chose the name old boy because I thought that I must be one of the oldest bikers around.
Since then I have found that a lot people have never given up or are born again bikers, anyone remember the Manor café at Blackwater or the Blue Hut at Basingstoke?
The picture is me with the type of helmet drawn on, that was worn when I first got into biking.
Added the glint in the eye as an indication that there's still a bit of life left in the old dog.
Used the Gimp software on a Linux box to make it.

And getting back to the silencer, this is a sketch of the Motad section drawn from memory, I think I have missed a length of perforated pipe going into the inlet end.

Jim, from the picture you have posted the tail pipe on your silencer looks a larger diameter than my 500 one, perhaps the 750 silencer is not quite so restrictive. Before mine rusted out the last ¼ or 1/3 throttle opening did not make much difference.