Muffler fabrication

[Guest]

G'day all,

I've finished knocking up an account of how I made the muffler for my GS1000S, here.

Hope it helps,
Mike.

[oldschoolorange]

thanks man that was really cool

[Bopi]

nothing I could say would reflect the tremendous amount of effort you have put in to not only the muffler fabs but the extensive details posted on your web site. Outstanding.

I'm still trying to figure out the math ( and don't tell me)

( its incredible the lengths some of these (you) guys will go to complete a project)

[Nerobro]

This is exactly what I needed to see. AHRMA won't let you use cans..

[snowbeard]

wow, I like the way you think!!

I have a couple ideas that I can't help but add, take or leave them, you've already outstripped my dedication to the project!!

I would think the whole purpose of the muffler is to force the exhaust thru the little 2,000,000 holes of the internal pipe, thru the packing and out the other side. i.e. would it work to weld a cap on the end of the internal pipe and also drill holes in the smaller reverse cone?

that said, maybe you could just cap the internal pipe and let the outer reverse cone be "free" from the internal pipe? that would force the exhaust thru the holes and packing and maybe, instead of holes in the reverse cone, it could have a way to suspend the internal pipe without making it vibrate and rattle all horrible like, but still allow the expansion lengthwise?

and I particularly enjoyed your disclaimer, a good hard laugh makes the life last longer!

[tfb]

G'day Snowbeard,

Basically there are two kinds of mufflers: the type I have made, with the 'straight-through' route for the exhaust gases. The advantages of this kind of muffler are:
1. Simple construction.
2. Very little impedence for the exhaust gases, corresponding low back pressure, and therefore maximised power.
3. Fairly effective sound absorption. This is achieved not by the gases having to pass through the fibreglass, but rather the sound waves alone are absorbed by the fibreglass. So, the 2,000,000 little holes aren't there to allow gas through -- but only to allow the sound waves to enter the fibreglass and be absorbed, never to be heard of again. The gases, however, just travel straight up the central pipe. :-D

The other kind of muffler is like your average car muffler, and most OEM motorcycle mufflers. These employ a tortuous route for the gases around a number of steel baffles, and through a number of seperate chambers, before the exhaust gases and any left over sound waves make their exit. Advantages:
1. Very effective sound absorption -- much more so than the 'straight-through' type.
2. And, err, that's about it. There is much more back-pressure with this type of muffler, and a corresponding loss of power. And, to accommodate all those bafflles and chambers, they have to be BIG. Which is OK on a car, but on a bike, well... the heeee-yooge OEM muffler on, for example, a FireBlade just looks daft.

Any muffler design which did what you propose, ie. push the exhaust gases through the fibreglass material, simply wouldn't work. For example, try stuffing a rag down the end of your muffler, and hold it there while you try and rev the engine. It will bog down and stall (if it didn't the moment you shoved the rag in). Which isn't what we want!

We want sound absorption while at the same time allowing the freest breathing possible. The 'straight-through' muffler allows for the best of both worlds.

[Jethro]

Wow, nice work there. Very impressed!

[Nerobro]

To say the least, glasspacks are tried and true. The muffler on Skreemers bike is just the same as this, but much, much smaller. Most "can" style mufflers are built like this. Most dirtbike mufflers are also like this. That is a perforated tube down the middle of fiberglass batting.

They're definitely a happy thing.

And something for me to copy. *giggles*

[saddlewarmer]

My question is: Is some kind of spark arrestor needed for this setup?

[tfb]

My question is: Is some kind of spark arrestor needed for this setup?

That's something I've never even thought about.

I think if your road bike is blowing sparks, then it's not tuned correctly, maybe running too lean, and prone to burning valves, etc.

But if you were going to be using the muffler on some trail bike or something offroad, where setting fire to nature is a risk, then that's a different matter.

In any case, on a GS/GSX machine, the combined headers+muffler is sooooo long that if any sparks made it to the end, that'll be the day that hell freezes over. :-D

[tkent02]

Sparks...

I think if your road bike is blowing sparks, then it's not tuned correctly, maybe running too lean, and prone to burning valves, etc.

One night riding home from work, three or four A.M. or so...
I 405, from Belleview up towards Everett.
Couldn't keep up with my buddy's Norton. He was running flat out because it had never run correctly before, we had tuned it up before work that day. He had never had it running properly before, had no idea. He was a happy man, on a happy bike.
I was laying on the tank of the 550, doing all she had for quite a few miles.
He was a long way ahead, when I started seeing little red glowing balls bouncing down the road. The faster he went, the more little balls were coming out, and the faster he went.
He got small in the distance. Real small.
When I got to his house he already had a beer out.
Said he couldn't believe it, it just kept getting faster and faster.
And faster.


So yeah, a road bike can blow sparks. Or glowing balls.

[tfb]

"Great balls of fire..."

Either
(i) that was the bike de-coking and they were burning flakes of carbon flying out, or...
(ii) it was burning bits of valves. :shock:

[tkent02]

I think it was the pipes de-cokoing themselves...

"Great balls of fire..."

Either
(i) that was the bike de-coking and they were burning flakes of carbon flying out, or...
(ii) it was burning bits of valves. :shock:

All 29 lbs of it. A lot of fireballs came out.
That Norton flew the next day and everafter as far as I know, so the valves must have been fine.
That thing would pull your elbows out of the socket if you whacked the throttle too quick.

[makenzie71]

A lof ot older bikes, if they still have the stock exhausts, after you stick them with propper jetting will literally blow flaming chunks of ash and soot out.

My TL throws all kinds of flames and sparks out so it's not hard to do, nor uncommon. Hell I can make a lot fo stock bikes do it...high rpm throttle chop works good.