Supertrapp motorcycle slip on installation how-to. Replacing that awful Muzzy!

[kz550]

Remove the old muffler. In this case a CF Muzzy that's held in at two points, the bolt on the passenger foot peg and a squeeze clamp at the mid-pipe.



Measuring for good measure. The Supertrapp aluminum racing series universal muffler has a 2" ID and a 4" exhaust OD at the diffusers. The inner core is a straight 50 MM ID, while you can see the expansion chamber shape of the muffler itself is that of a megaphone.


There's a pin that will go through the Supertrapp muffler and the mid-pipe, just as I've done on my other two bikes. See below for more.

[kz550]

Use a round sided metal file to smooth out any burrs or imperfections to make for easier mounting and a more snug fit over the mid-pipe. Do not file the aluminum, just the steel inner core, which is how the Supertrapp's muffler matches the 2" ID.

Set the orientation of where you'd like the Supertrapp logo to appear. I prefer slightly rotated upward from level, which coincidentally puts the top of the tri-pins at the back of the muffler at just before the 12 O'clock position. *Trick* hold the muffler while it is still wrapped in the plastic bag it came in to prevent getting fingerprints on the aluminum surface.


Next, orient the retaining clamp over the mid-pipe and the Supertrapp muffler over the mid-pipe to verify fitment. Note, the squeeze clamp is on incorrectly. The nut faces the other way.


Not that this is the only way to do it, but I also give the squeeze clamp an initial tightening to make it easier the second time coming up.

[kz550]

I skipped a step in the photo sequence. This shows the muffler pulled back after aligning the muffler's final position over the mid-pipe. The hole is initially drilled through the aluminum and steel of the Supertrapp and hopefully through the stainless steel surface of the mid-pipe, but it was too hard for my drill bits. So, I pulled the muffler back a half inch or so to continue drilling into the pilot hole created. This is the resulting 1/8" hole made for the dowel pin.


I pulled the muffler back still further to allow for reaming of the two holes. The pin's diameter is slightly thicker than 1/8." A 1/4" drill bit is used to bevel a resting area for the pin's head.


That's better. Pin sits flush with the aluminum mating surface, which will be under the clamp. Now just remove the pin, move the muffler forward to align the holes up and drop the pin in again.

[kz550]

Like so. Now slip the squeeze clamp over the compression zone at the front of the muffler.

[kz550]

Approximating which region of the muffler the mounting plates will be welded. They have to be bent first as well, a process that usually takes a skilled welder about half an hour to perfect.





She'll never look cleaner.


An initial startup of the bike was actually only slightly louder at idle, but I could still hear from memory the old Muzzy's exhaust note at idle. Everything above idle gets progressively more pronounced in dB.

AFRs are much richer (max rich) in the current exhaust configuration at low RPM, but carburetion or something mechanically amiss still haunts this bike. I want to believe it's something in the carburetors and probably related to the pilot air jet passage, if I had to guess.

[kz550]

Brackets welded and mounted.





But there's always a compromise. Yes, I love the appearance. Yes, the power is better already, both mid-range and top-end. Mid-range still isn't right though. And I can see from the UEGO that fueling could be dialed in for better performance. The issue is trying to nail down some inconsistent throttle readings that persist.

The bad is that slapping exhaust sound I was hearing when the Muzzy CF muffler was on there while rolling the throttle, has changed to something else. That sound is coming from the SS pipe's layout. The 4-2-1 makes the bike sound like something between a hybrid crossplane R1 and an EX500 twin, both of which I find uninspiring to the ear. Really?! Nobody ever noticed the sound difference between a 4-2-1 and the stock header's screamer note? When I first rode it tonight I though it sounded sick, but not in a good way sick. It sounded like it was running on two cylinders sick. And this 2" ID Supertrapp, having the smallest internal area of the three, is by far the loudest...and now also the most obnoxious.

On the performance side this is still the only bike of the three that gets leaner AFRs when I roll the throttle 1/4 - 1/2 open from cruise, before they go richer at 3/4 - WFO, making jetting changes extremely difficult to determine. I'm fairly certain that the aftermarket jet kit needles need to be replaced with stock ones. All the power is still packed way up top too, difficult to access unless the bike is always wound up. It's not stalling like it once did, so I suppose I should be happy with the progress. What an embarrassing nightmare that used to be!

I'm sure I'll figure it out eventually. I'm just a little bummed that I sunk money into the 2" aluminum Supertrapp now that I know I may have to replace the Muzzy exhaust pipe with a stock unit, which only works with the 2.5" aluminum Supertrapp.