This 4x4 exhaust system was first introduced on the CB500s and continued on the CB550Ks up 'til 1977, when they were given a major revamp (more on this later). These are the stock "HM323" pipes, and were marked "CB500" even after the 500 evolved into the 550... they are still correct for the CB550 application, and remain unchanged from the CB500s; the two are, in fact, completely interchangeable. Installation is fairly easy and straight forward... the only real difficulties are mainly due to their size and weight, making them somewhat cumbersome to fiddle with. This is how I installed them on my bike; this is not the only (or, possibly, the best) way to do it - some like to install at the head first - but at least the following will give you an idea of what's involved.
Here they are in nice, sparkly new condition with the mounting brackets and center stand cushion (inset) already installed
I got these from BikeBandit a couple of years ago and paid something like $700 - $800 for them; nowadays, since they're no longer being made, I've seen people wanting stupid crazy prices in the thousands of dollars for a set like this. At this point, they may be the most valuable part of the bike...
Here's a look at the hardware I'll be using to mount the pipes
From top to bottom are the exhaust mount "joints", below those are the joint spacers (or "collars"), then the four copper gaskets, the mounting nuts and split washers, the rear mount bolts, and the balancer tubes and clamps. Smack in the middle bottom, trying to remain inconspicuous but failing miserably, are the passenger foot rests, which I'll install along with the pipes.
I began by inserting the copper gaskets into the exhaust ports
These should fit snugly and hold themselves in place by frictional pressure; if they're loose and won't stay in place, check to see that you have the right gaskets or, more likely, the old smashed up gaskets are still in the port and need to be removed. Gaskets in the ports are a relatively common malady that can cause all kinds of mischief because it's not always obvious that they're still there; they kind of get squished flat and can appear to be part of the port. The gasket area around the port should be flat with no ridges or steps. If you do find old gaskets in your ports, they're easy to remove using a flat-bladed screwdriver.
Now comes the fun part: installing the pipes themselves. I began by laying them out in order on each side of the bike. It's easy to tell which pipe goes where if you follow a couple of simple rules: first off, the mounting brackets are oriented inward toward the bike, so that'll let you know which pipe goes on which side of the bike; and, secondly, the balance tube flanges extending from each muffler should point toward each other, so that lets you know which pipe goes on the bottom (inside) and which on top (outside). The top pipes are installed on the outer cylinders (NOs 1 & 4); the bottom pipes on cyls 2 & 3. Simple enough. The longer mounting brackets are installed on the bottom pipes, while the short ones go on the uppers...
Next, I "hooked" each header in the exhaust port openings so that the pipes were oriented roughly in the correct position. The flange on the end of the header is caught by the port opening and fins and will hold the pipe in place while it's being attached at the muffler
One thing to note about the above photo is that I've slid the joint for each pipe down onto the muffler so that it'll be ready for later. Once the rear mounts are attached, it's nearly impossible to get these things on, so now's the time to install them. They should be oriented so that the step in the joint "face" is pointing forward (inset). It seems like it would be a good idea to actually mount the joints onto the studs at the port, thereby aiding in holding the pipes in position, but doing so causes the pipes to bind and makes installation at the muffler difficult, so they're just sitting there for now, patiently awaiting their moment in the spotlight, all the while tossing out crude remarks about trains going through tunnels, ring toss, and other vaguely suggestive observations of a questionable moral character...
With everything in place, I inserted the rear mounting bolt (with washer) through the hole in the footrest bracket (below right, inset), then through the corresponding hole in the top (outer) muffler bracket (in this case, pipe #4). Pivoting the pipe upward, I aligned the bolt with the hole in the frame mount "ear", then pressed it through, entrapping both brackets on the outside of the "ear". With the bolt holding everything in position, I prepared for the next step by installing the balancer tube and clamp onto the flange on the bottom (#3) muffler (inset)
This next bit is a real juggling act. As the bottom pipe is raised into position the header flange must stay in place in the port while the muffler bracket is inserted from behind onto the mounting bolt extending from the rear of the frame mount "ear". Simultaneously, the balancer tube is slipped onto the flange protruding down from the top muffler, entrapping the tube between the mufflers. It all happened so fast that I'm not really sure how I accomplished this feat, but I think I withdrew the mounting bolt until only a slight nub protruded from the rear of the "ear", inserted the balancer tube up onto the flange in the top muffler, and then pressed the bolt on through the hole in the muffler bracket. There's a bit of finagling to do in order to get everything into the proper position, but once it's there it's all held in place with a loosely installed nut and split washer (inset). I don't want to tighten anything down yet as I'll need some "wiggle" room for the next step
Something to note in the above pic, especially in the inset, is that the frame mount "ear" is sandwiched
between the muffler brackets: top in front, bottom in the rear.
I began the final procedure by sliding the joints up the header to their position at the port. The collars are installed around the pipe with the flanged end toward the joint, where they slip into the "step" described earlier. The other end butts up against the flange on the header (inset). As far as orientation of the collars is concerned, Honda doesn't really specify how they should go, either vertically or horizontally; I've positioned them vertically after a forum member suggested they might drain water better that way... makes sense to me, so that's how I've done it
Now, the pipes will have some manufacturing tolerances to them and those big copper "O-rings" take up a lot of space, so when it comes time to slide the joint/collar/header assembly into place in the port not much of the stud is left exposed behind the joint for the nuts and split washers to fit onto. The trick here is to install the nuts, torque them down to specs, then remove them one at a time so that the washers can be added. You don't want to forget the split washers as they're a safety feature, and it's not a good thing to have your pipes coming loose in the middle of a run...
Right side complete; time for the other side, where it's "second verse same as the first" (and if you know what song that line came from and can even sing a couple of bars, you
are old...)
The final step, with everything properly fitted, is to tighten up all of the nuts and bolts I've left loose, finishing up with the screws on the balancer tubes
And there we have it: shiny new pipes for the bike. Here's a shot of the completed installation
One thing to mention regarding interchangeability: while the CB550 and CB500K exhaust is interchangeable, that doesn't hold true within different years of the same model bike. Due to frame modifications, the exhaust for the '77-'78 "K" bikes will not fit on the pre-'77 frames without some fairly extensive modifications involving hammers, drills and other implements of destruction; and vice-versa. While it definitely has been done, I wouldn't want to take on the task. The right accessories for the correct applications is the way to go, IMHO.
Here are some shots comparing the number 1 exhaust from an early (pre-'77) CB550K and a later ('77-'78) bike just to illustrate some of the differences
More to come, so check back for updates.
'til next time
