I have a 1981 Honda CM400T. The mufflers (slip on) are probably as old as the bike and in serious need of replacement. It took me a long time to even find a resource to replace them with a brand new pair, but heard about retrofitting a Harley Davidson slip on, namely Sportster, instead. These two links are helpful, as long as they still work, for how I got started.
http://www.advrider.com/forums/showthread.php?t=131699
http://www.youtube.com/watch?v=XCGJJghf32s
Tools needed are the appropriate sockets or wrenches for removing your slipons to begin piecing together your upgrades. I have a Harbor Freight 90amp DC welder, drill, and I used channel lock pliers to manipulate the flanges on the sending and receiving end of the muffler.
Known dimensions before I got started were this. I needed something that would go into 1 and 3/4 inch. That is the dimension of the collector box bellow where the slipon will get wedged into.
2nd, I kind of knew how long they should be. The original slipons were 19" I think the HD's are 24". Not bad of an extension if you are trying to make something of how it looks with the chrome. I wanted it quieter. And, as it turns out, you need proper working mufflers so there is proper back pressure. It helps the carbs work like they were designed and so the exhaust doesn't rush out too fast and burn up your valve.
Below are pictures showing a succession of photographs taken during the process. I will write notes underneath some of the photos to describe in detail.
Original picture before I got started to study the path the new muffler will take.
I paid 85.00 plus tax for these used mufflers and had a receipt. Any issue with fitment before you begin grinding, welding or basically making them unreturnable can be avoided at this step.
The original bracket will not fit the new muffler, modifications will be necessary.
The side port will be in the way with this project and will soon be cut off and welded shut with a piece of sheet metal I already own.
Not going to fit.
Still in a returnable condition, the first installation is made and the angle that it protrudes is studied. How will I adapt it, what materials do I have to modify.
It's pretty easy to see how this will work once you understand what you have available to make it work.
I am looking at the foot peg/muffler mount and the way the new muffler aligns to it. It's hard to see in the shadow, but I am going to adapt the hefty metal of the muffler mounts.
I crimped the muffler together to help it in placed.
Aside from this modification's success, this is my favorite picture. It is a display of all of the metal I have come into to scrap. As I get calls to collect scrap, I choose prime scrap for future projects like this one. This represents approximately 400.00 worth of material if you bought it at the hardware store.
4" cutting wheel on my grinder.
More room to twist it around as necessary without that side port hitting other components
This is a length of 5/16 round stock roughly measured to each side of the muffler mounts.
Before welding, so you don't have to cut it off. Look at potential benefits to where it is welded.
Will it interfere with anything after it is welded in place. Though it can be ground off, who wants to do that when you could be making progress.
It so happens that if I weld in the location shown, I will be able to put a piece of 3/16 flat bar with a hole in it, straight to the 5/16 round stock and weld it in place.
If you look at the piece of metal I cut out on the right. It is sitting on the metal that I cut it off of.
It is 16th of an inch sheet metal and will patch that side port nicely. All of the gauges well within the parameters of a 100.00 mig welder.
I don't know what this was, some sort of bracket for something. But, I know what it is now. It is donor metal for connecting the 5/16 round stock to the foot peg/muffler mount.
Drill a hole in the rectangle you just cut off that is capable of receiving the bolt for the foot peg/muffler mount.
I moved the muffler with the 5/16 rod already welded on, up to the rectangle, eye balled it, double checked it's trajectory from the collector box and tacked it in place. I don't like to use the grinder to change my mind. Tacks are also a good way to check it before you proceed further.
Additionally, it's easier to weld extensively away from bike to keep the dingle berries off of it, and not chance ruining a nice paint job.
This is piece of scrap sheet metal protecting the muffler from welding the bracket.
In this case the metal didn't warp that much. Keep in mind that running a long weld bead might change the angle you intended to weld to the point you can't bolt it on. Clamp it in place or tack it in several places so it minimizes warpage.
Painted the welded surfaces as they were bound to rust later if I didn't.
This is how the other side started. Sometimes after 30 years, it just isn't going to come off like it went on.
My mufflers were so worn, my guess is they were 4x quieter. It starts easier too. As far as re jetting, it's my understanding that replacing with stock slipons it does not require it. Your spark plugs can be used to determine whether it is too lean or not. If it's running rich, they will be black. There are plenty of web pages describing the condition of a spark plug.
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