Bill's CH125 Website

Muffler / Exhaust Repair

After some days of searching, it appears that no "OEM" exhausts are available. A Yellow Pages search for "Welders" in the (423) area code listed a couple of dozen.

In a past life I worked in the design and sales of very large petroleum equipment, and worked daily with 50 to 100 highly skilled welders. I'm not a craftsman, but I am familiar with the kinds of work done. From that experience, I knew that most large companies would probably not be willing to undertake a small odd job at a reasonable price.

(Right) I ended up at AES Manufacture here in Chattanooga, Tenn. -->

One look at that sign tells you that Steve Morgan is an artist - and his business card says in bold caps; "SMALL WELDING REPAIRS WELCOME." This is my kind of place!

There's my muffler, about to undergo surgery without anesthetic.

Patrick is a top-notch welder in addition to being generally handy with a wide range of power tools. With his sometimes caustic advice, I elected to keep the cutting to a minimum.

We decided that whatever was rattling around was in the forward expansion chamber, and we were right, but as it turned out, the muffler is a whole lot more complicated device than you might think!

A small high-speed abrasive wheel was used to cut along a line around the "shoulder" of the expansion chamber.

Remember the two spot welds mentioned above? We found that those had to be isolated as well, to permit the outer skin of the muffler to be removed.

Inside the outer sheet metal there was a thin layer of compressed fiberglass wool, and inside that, the perforated sheet metal seen here. I surmise that the idea was to provide added cooling and expansion and to prevent the "box" from resonating at some undesireable audio frequency.

Bending aside the perforated sheet allowed me to shake the muffler until the loose part fell out.

That's it. Apparently intended to guide the exhaust gasses into a more-or-less circular flow inside the expansion chamber, it should have been welded at the end of the incoming exhaust pipe.

Close examination shows that the manufacturer's welder had burned through the item, leaving it hanging by a tiny thread of steel. We could have replaced it by opening the muffler still more, but I decided this was unnecessary.

Anyone need a tiny scooter fender?

Here's the finished job. Although some "rust" shows, there is no pitting or internal corrosion. The exhaust pipe and muffler are essentially as good as new. Another small previously repaired "leak" was rewelded, visible here on the left side of the muffler-exhaust pipe.

Lacking that internal "guide" and some of the fiberglass mat, the the muffler's life expectancy may be shortened, but, in my estimation, not by much.

Before re-mounting the exhaust, it will be wire-brushed and painted with "heat resistant paint" from my favorite Ace Hardware store (Ace 17066 Aluminum.)

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Muffler / Exhaust Repair
When the 1984 Elite was purchased, the seller warned me that the muffler was bad. Unfortunately, there are no new replacements available in the Honda parts system, and a search of "motorcycle junk yard" Web pages failed to turn up any mufflers. Doug Simpson's excellent scooter pages contained a sketch of a design for a replacement exhaust that would probably be fairly easy to construct (if I had a heli-arc welder and a tubing bender,) but a local welder offered to fix the old muffler for (in his words) "... a lot less than building that new one..."
With the help of the "Shop Manual" the left side panel was removed. What you see here is mostly heat shielding. The exhaust system is still a long way from being removed!
Here's the removed exhaust. The close proximity of plastic body panels and the suspension shock absorber demands that heat shielding be used, essentially identical to the original design. This makes it desirable to repair this muffler rather than fabricate a replacement.
The in-side of the muffler (toward the wheel) reveals two expansion chambers. The leftmost chamber contains a loose part, rattling around like a marble in a tin can. I guessed that the spot welds (barely visible here) held baffles that force the exhaust gasses into a longer path for cooling and expansion to reduce the noise level. Note that the exhaust-engine connection (upper left here) demands a crushable (composite metal-asbestos) gasket - there was none in place when I removed the exhaust. Since the overall condition is not bad, that left chamber will be cut open and, if possible, the loose part re-welded in place, then the chamber welded back together. This keeps the critical mounting points correctly located, so that the heat shield and exhaust system mounting will work as designed.
After some days of searching, it appears that no "OEM" exhausts are available. A Yellow Pages search for "Welders" in the (423) area code listed a couple of dozen. In a past life I worked in the design and sales of very large petroleum equipment, and worked daily with 50 to 100 highly skilled welders. I'm not a craftsman, but I am familiar with the kinds of work done. From that experience, I knew that most large companies would probably not be willing to undertake a small odd job at a reasonable price. (Right) I ended up at AES Manufacture here in Chattanooga, Tenn. -->
One look at that sign tells you that Steve Morgan is an artist - and his business card says in bold caps; "SMALL WELDING REPAIRS WELCOME." This is my kind of place!
There's my muffler, about to undergo surgery without anesthetic. Patrick is a top-notch welder in addition to being generally handy with a wide range of power tools. With his sometimes caustic advice, I elected to keep the cutting to a minimum. We decided that whatever was rattling around was in the forward expansion chamber, and we were right, but as it turned out, the muffler is a whole lot more complicated device than you might think!
A small high-speed abrasive wheel was used to cut along a line around the "shoulder" of the expansion chamber. Remember the two spot welds mentioned above? We found that those had to be isolated as well, to permit the outer skin of the muffler to be removed.
Inside the outer sheet metal there was a thin layer of compressed fiberglass wool, and inside that, the perforated sheet metal seen here. I surmise that the idea was to provide added cooling and expansion and to prevent the "box" from resonating at some undesireable audio frequency. Bending aside the perforated sheet allowed me to shake the muffler until the loose part fell out.
That's it. Apparently intended to guide the exhaust gasses into a more-or-less circular flow inside the expansion chamber, it should have been welded at the end of the incoming exhaust pipe. Close examination shows that the manufacturer's welder had burned through the item, leaving it hanging by a tiny thread of steel. We could have replaced it by opening the muffler still more, but I decided this was unnecessary. Anyone need a tiny scooter fender?
The internal (perforated) panel was tacked in place, and I decided not to try replacing the fiberglass; then the removed exterior piece was first tacked, then continuously welded back in place. Pat did a great job on this not-so-easy welding. A slipup here could result in burning through the muffler's shell, making a difficult repair. The completed job is a work of art - even though Pat complained that "...it should have been better." Personally, having worked for years with many "code" welders and ASME inspectors, I didn't see much room for improvement.
Here's the finished job. Although some "rust" shows, there is no pitting or internal corrosion. The exhaust pipe and muffler are essentially as good as new. Another small previously repaired "leak" was rewelded, visible here on the left side of the muffler-exhaust pipe. Lacking that internal "guide" and some of the fiberglass mat, the the muffler's life expectancy may be shortened, but, in my estimation, not by much. Before re-mounting the exhaust, it will be wire-brushed and painted with "heat resistant paint" from my favorite Ace Hardware store (Ace 17066 Aluminum.)
A wire wheel chucked in my portable drill made easy work of cleaning the exhaust system - wearing safety glasses of course. Before painting I wiped it down with paint thinner. This is one thin coat of paint - I'll update this page in 6 or 7 months to see how well this holds up. Although the paint is rated at "...1000F intermittently" you could smell it burning after a ten minute ride.
There was a broken stud in one of the mounting points -- no surprise to any experienced owner of an "old scooter." I center-punched and drilled it, then tried to back out the stub using a screw extractor. Guess what: the cast "ear" broke before the busted stud came loose! Fortunately this didn't damage the engine casting, so this one mount is unused. Threads in the other one (barely visible below) were buggered up, so I used a smaller machine screw, washer and nut there. After installing the exhaust, I found that the inner heat shield rattled against the rear suspension spring. A couple of 4 or 5 mm spacers moved the muffler outward enough to stop that noise.
The muffler was missing its essential exhaust gasket when I bought the scooter, so I ordered two from my local Honda dealer. These $3 items are "crushable" gaskets, only good for one use, so it's essential to have a spare. If you've never worked on one of Honda's "plastic wonders" you don't know the joy of putting several locking tabs, snap-in-studs and bolt holes all in place in the proper sequence. If any Honda engineers or representatives see this, let me just say one thing: YOU HAVE OVER-ENGINEERED THE BODY PANELS FOR BEAUTY, AT THE EXPENSE OF EASE OF MAINTENANCE! There - I've said it and I'm glad!
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