New muffler

[tfb]

Just thought I'd like to share with you all the new muffler I made for my GS1000ST. I wanted a classic look, but with better breathing (and cheaper price!) than the Dunstall replicas etc. out there.

So with the help of my TIG-welding mate over the road, this is what we came up with:

It's made out of 1mm sheet steel, around a 2" diameter length of exhaust pipe, packed with fibreglass roofing insulation(!), TIG-welded together, and given a coat of matt-black exhaust system paint. Very quiet, with a deep-ish note as well.

All-in-all, I'm pretty happy with this, esp. as it's a first effort. Now to see if we can make one out of stainless steel...

 

[80GS1000]

Very nice. especially for a first effort! Got another pic of the bike, maybe from behind?

 

[Guest]

That looks very clean!! Nicely done, sir!! \\/

 

[johnnay]

Very nice!! did you have to perforate the 2" pipe, or were you able to buy one already perforated? Must have taken a while if the former...

 

[jetta90]

That looks very, very good. Well done. If you get a chance post more pics please.

 

[tkent02]

How did you roll the megaphone section???

How did you roll the megaphone section???

Looks sweet...
Production pics and tips would be wonderful.

 

[Bopi]

yep...........Nice piece of fab work.


How bout some close-ups

"fifteen percent inspiration, 90 percent perspiration and thirty percent disposable income"
(Yogi Berra meets Thomas Edison)

 

[tfb]

Thanks for the encouraging feedback, folks.

did you have to perforate the 2" pipe, or were you able to buy one already perforated? Must have taken a while if the former...

Yes, I did the perforations in the pipe myself... rows of 5mm holes at 10mm spacing (centre-to-centre), running from a couple of inches inside the exit end, to a few inches from where the cone taper meets the engine end of the muffler. It took me a couple of hours slogging with the drill press... but it was a hot day, the low alc. icy-cold beers were on hand, and I just kind of got IN THE ZONE. :-D ... if you know what I mean.

Production pics and tips would be wonderful

They will be getting posted on my website in due course (can't make any promises when, exactly), along with formulae etc. for translating the truncated cones (there are two which make up the outer skin of the muffler) to flat shapes, so that you can cut out the steel.

How bout some close-ups

OK, when I get a spare moment I'll take some more pics. But bear in mind that this is a first attempt, and I kind-of almost deliberately didn't take any really close shots!!! The only aspect I'm not happy with, and will attempt to get right with muffler #2, is that when you look at it end-on, it's not a perfect circle, ie. a bit out-of-round where the two cones meet at the widest point of the muffler. Otherwise I make no apologies!

 

[gsgeezer]

I would love to be able to do that on a first effort!

 

[tfb]

I would love to be able to do that on a first effort!

Well, I must say I was pleasantly surprised too!

I think the key things for it turning out so well were:
1. Simple construction. It is three pieces of steel: (i) the pipe up the middle bored full of holes, which extends out the end enough to locate into the exhaust system; (ii) the short truncated cone on the end of the muffler; (iii) the long truncated cone making up the rest of the muffler exterior.
2. Accurate cutting-out of the sheet metal. This was simply a matter of calculating and tracing out the shapes I wanted, and then taking my time with the jigsaw. (I had a metal-cutting blade on the jigsaw, of course.)
3. Carefully bending up the cones from their flat shapes. This was the biggest challenge. Now, my mate over the road has some metal-rolling equipment in his shed, so that was a *great* help getting things started. Then we got it into final shape using a wooden 'mandrel', ie. wooden cone of the final muffler shape I wanted, and we used a number of large hose-clips to bend it and coax it so that the length-ways edges of the cone met, before we hit it with the welder.
4. Welding it up neatly. We used a TIG welder for this, but MIG would have probably been just as neat.

Here's a couple of extra pics from the rear, as requested:

And now looking straight down 2 feet of pipe. You can almost see the valves from here...

 

[dardoonk]

Nice job, definately looks as it will flow well. That's half your objective. How much $$ do you have tied up in whole thing?

Always remember the Do It Yourself Costing Rule:

:razz: "The price of Beer & Snacks shall be included as the cost of labor"
​

 

[tfb]

In Australian dollars:

• $30 for the sheet steel (a 900x1200mm sheet, enough to make 3 mufflers!)
• $15 for the length of 2" diameter exhaust pipe
• $10 for a short piece of exhaust pipe with a bend in it (which I needed to route the muffler into the existing exhaust system)
• $0 for the fibreglass wadding (roof insulation) -- mate up the street supplied this
• $0 for the welding -- another mate over the street
• $20 for the can of hi-temp spray-paint
• $2 to make a threaded plug from an 18mm nut & bolt (to accommodate the O2 sensor for when I'm doing diagnostics with my AFR meter)

So there you go, less than $80.

But now then, if I factor in the beers, and also the beers I MORALLY owe all my mates up and down the street... err, it's priceless! :-D

 

[mixongw]

Not to throw cold water on a great muffler... But is there any way to replace the fibreglass packing? Great looking muffler at any rate.

 

[tfb]

You would have to dremel open the end, and then TIG it back together -- I can't see it being a big problem.

 

[dardoonk]

So there you go, less than $80.

But now then, if I factor in the beers, and also the beers I MORALLY owe all my mates up and down the street... err, it's priceless! :-D

$80 bucks & you could have made three pipes... sweet deal.

Paying in beer-dollars is always less expensive, but the quality of work always seems to go down the faster you pay them. :? It's probably best to cash out after the work's done!

Nice job on the pipes

 

[tfb]

OK, here's an update on the muffler.

So far I've done about 1000kms (600 miles) on it. It's going really well except...

... except there is a crack running around the end of the muffler, where the shorter 'end cone' meets the 2" central exhaust pipe at the exit. :shock:

At first I thought it was just a dodgy weld. But today I noticed that when the muffler is hot, the pipe protrudes about 0.5mm, and when it's cold it goes inside the end of the cone about 0.5mm

In other words, the cracking is caused by the central pipe expanding at a greater rate than the external muffler sleeve.

So, the first design improvement on future mufflers I make, will be an internal expansion joint.