obriencj

is a pile of bits

RSY Beauty Megaphone
a new exhaust for Tux

I’ve been wanting a new exhaust for Tux for a while now. The factory muffler is enormous, heavy, tends towards rust at the end, and is effectively silent in traffic.

I’d tried out the inexpensive slip-on Mini-Norton from Dime City Cycles, but it was too flipping loud (distractingly so while moving) and it required a full stack of adapters (and tape!) to make it fit Tux’s small diameter exhaust pipe. It also required me to craft a bar to support it from the frame, leaving it somewhat unstable and putting more force on the exhaust header screws than I am comfortable with. I ran with it for a day, but retired it due entirely the sheer ear-wrecking volume.

The Beauty

Some time later I happened to run across photos of the RSY Beauty. It’s designed specifically for the ST250 (which is the JDM version of Tux), so it had mounting hardware in the right places. It was rated at a sensible 89dB, and it looked very nice. Promising!

I ordered it from Web!ke as an early Christmas present for myself, and was surprised to discover upon its arrival that it was actually a full exhaust system, not just the muffler. The exhaust header is stainless steel to match the muffler. It has some built-in baffling just after the port for the lambda probe. The muffler itself has only a minor cage baffle, and is very lightweight. It has a tab that fits with the existing mounting bracket perfectly. It’s louder than the original muffler (which was ridiculously quiet), but not ear-bleedingly so like the Mini-Norton was. It has an overall pleasant tone, nothing too tinny or sputtering. It does suffer from an occasional roll-off pop, but that isn’t a huge deal.

I recorded a short video of my kicking Tux over so people could get a feeling for how she sounds now.

Problems

Unfortunately, after around 150 miles I concluded that there was a definite resulting lack of mid-range responsiveness, and a major decrease in fuel economy. Uh oh. I postulated that the reason was that the in-built baffle was too restrictive – it had a total of six holes along the sides, which were very narrow and only perhaps a centimeter from the sides of the pipe.

I also noticed that exhaust pipe appeared to be getting hotter than the original pipe. It discolored quickly at the head bend. It was easy to feel heat radiating off of it, and you could clearly see the distortion from heat waves. The original pipe was double-walled and chromed, so it kept a lot more heat in the exhaust.

I was not prepared to give up so easily, so I decided to make a pair of modifications. Firstly, to wrap the header to keep the heat discoloration hidden. Secondly, to drill a small hole straight into the end of the embedded baffle to provide a small amount of direct flow.

Exhaust Wrap

I ordered a 50’ roll of 2” fiberglass wrap from Amazon, along with some black high-temperature silicone paint and a few extra steel ties.

I removed the pipe, gave it a cursory cleaning and wiped it down with mineral spirits and a clean rag. I soaked the wrap as instructed, and began wrapping it tightly from the lambda-probe port forward, with 1” overlaps. It was finnicky business, and I had a few false-starts, but eventually I got a decent looking tight wrap and I tied it off to hand tension.

The wrap was still dripping wet when I re-installed the pipe. I worked the wrapping a bit by hand to further tighten it, moving the miniscule amount of slack upwards towards the head, wringing it out a bit.

Then I fired up the engine, and let the heat from the idling engine gasses do their work. After a while there was a fog of steam smelling of hot starch. Slowly the steaming became less extreme, and I shut the engine off.

Thirty or so minutes later, I gave the exhaust another wringing by gloved-hand, and further tightened the wrap and my ties. Then I took Tux for a ride around some winding back roads where there was little traffic. Whenever I’d stop, there was still a smell of hot starch, but no obvious cloud of steam.

The next day, I checked, and the wrap was hard to the touch and still tight around the pipe.

Let It Breathe

After riding for a while with the wrap, I got up the gumption to start drilling. I removed the pipe and gave it a few quick sprays with the black silicone spray. The wrap had been bleached white from the miles I’d put on it, and the black darkened it back up where it belonged.

I took a 3/16” drill bit, held my breath, and put a hole directly in the middle of the baffle.

I took it for a ride to test it out and oh what a relief! The engine was much more responsive, it accelerated like it had before the switch, and hadn’t gained too much volume. Success!

Results

The RSY Beauty sounds great. It’s not going to wake the dead, but it’s got a good tone and slightly more volume than the stock silencer. It will definitely serve to help let someone know you’re passing them while riding. There’s a visceral feel to revving that engine to take off. It does pop every now and then (low RPMs, very little throttle), but those aren’t gunshot-loud.

The RSA Beauty on its own seems to strangle the engine a bit, and there is a definite drop in power and responsiveness. This means a lot for those who are running right at the edge of usable output. I’m currently running with a 16 tooth front sprocket and larger real tire, trading power for speed. Losing 2 HP hurts when you’ve only got 15 HP to start with. Drilling that small breather hole got things back to where they needed to be, and she’s once again a total joy to ride.

I can safely say that the exhaust certainly looks better wrapped, so I definitely recommend this as an asthetic modification. In theory, there is also a teeny tiny performance boost to keeping the exhaust gasses hot as they travel out through the exhaust (losing heat slows them down). In practice, without running the bike on a dyno, I have no way to ascertain whether this is actually beneficial to performance.

Change Log

  • 2014-12-13: Real write-up for posting
  • 2014-10-10: Original blog posting