Unfinished Business 6 – Stealthifying Risa

Too Much Attention

It was a lazy Sunday morning and I was on my way home after fiddling with the suspension settings. The bike was closer to what I would like her to be. Bobbing down the highway, I decided to take an earlier exit with a nice sweeping left hander to see how she would behave after the tweeks.

We proceeded onto normal roads and was riding leisurely at this point, my mind being only half awake. I was enjoying the nice engine and just burbling along at a traffic police approved pace. As we went past a junction, I spotted an enforcement bike (police version VFR800) parked at the side and the officer talking to a lorry driver. As we went past at a respectful gait, the officer stopped what he was doing, looked in my direction, and from the corner of my eye, I saw his gaze following us as we went down the road.

Risa was singing a little too loudly and the Mr Law Enforcement seemed to disapprove. I was not even riding in a remotely enthusiastic way and the revs were low. Even so, the noise that she made attracted the unnecessary attention.

Fly Under the Radar

Risa was not designed to be a commuter. No one needs 160bhp for commuting. With good suspension, more than adequate power and good brakes, it is almost certain that I am going to, shall we say, “enjoy riding it a little more”. I don’t know about you, but with a something like this, I would prefer to “fly under the radar” and the Yoshimura full system basically threw this idea out the window.

The offending muffler

It might have been fun in the beginning to hear the throaty idle and the roar when riding through tunnels, but I soon weary of the noise. Catching the ears of authorities also put a damper on my enjoyment. I have had the bike for a few months by now, but have not really opened up the throttle because of the noise from the pipe.

Proverbs 15:1
New King James Version


15 A soft answer turns away wrath,
But a harsh word stirs up anger.

Options

After the latest officer incident (and there were a few others before that), I decided that I needed to do something about this. Risa’s exhaust pipe is legal. It has been approved and registered in the enforcement system. I just wanted it to be less obnoxious and attract less attention.

To achieve this, I could 1) buy a full stock exhaust system – header, mid pipe and exhaust – and put it onto the bike, 2) have the exhaust re-wrapped, or 3) find a dB killer / baffle to use with the pipe.

Searching around the classified ads and ebay threw up some stock exhausts, but they were mostly headers. The OEM mufflers were not in good condition with high asking prices. The most difficult thing to come by seemed to be the mid link pipe. Re-wrapping the exhausts would not reduce the noise much it seemed. So I decided that the most budget friendly way to go was to find a diffuser that can work with the pipe.

No dB Killer for The Japanese Tri-Oval?

My Yoshimura muffler was a Japanese made Tri-Oval. I examined the diagrams but could not find a removable baffle in them. Going online, I found the Yoshimura Japanese website and saw the system there but there was also no dB killer part listed on their website.

I also noticed something that the website said that this was a race system for track use, so I checked the documents and diagrams again. I now noticed that it said the same thing. Hmm what’s with that?

Anyway, I looked a bit more and found the Yoshimura USA website with a similar looking Tri-Oval system that had a optional dB killer for sale. So I sent them an email with photos of my muffler and asked if I could install that into it. They replied that they are not sure and there was also no hole to fasten the dB killer.

I next went to the shop that originally sold the pipe to ask if they have something to use with this muffler, but was also told that there was none for it. They did try some baffles and see if they fit the pipe, but none did. In addition, the shop advised that if I were to drill a hole to secure the dB killer / baffle, the LTA might consider that as modification of the muffler and I might get into trouble (for making it quieter?).

Ali-Express Baffle

Meeting these dead ends, I decided to look around some more on the internet to see if there were other solutions. I was mostly resigned to look for an OEM system when I came across a curious item. It was a dB killer / baffle made to be inserted into the inlet of the muffler instead of the outlet end of the muffler.

Different styles of “Ali-Baffles”.

ZSDTRP 50.8mm 60mm Motorbike Universal Front Catalyst DB Killer Removable Silencer for Motorcycle Exhaust Muffler|Exhaust & Exhaust Systems| – AliExpress

I was initially hesitant about getting one like this as they were Chinese made and I was not sure how it would affect the performance of the engine. However, with few options left, I ordered a 51mm one. There were many different designs, but I decided on one with a “catalytic converter” style mesh at the inlet and a blocked outlet with big holes. I doubted that those with just a “catalytic converter” style will dampen the noise much.

Installation and Test

The Ali-Baffle arrived after a week or so and it looked alright. It was made from some form of steel and had a solid feel to it.

Removing the muffler was a simple job of unscrewing the bolt holding the can to the foot peg, unhooking the 2 springs pulling the muffler onto the pipe. The Ali-Baffle fitted nicely into the inlet of the muffler and I pushed the it back onto the pipe. It seemed to stay in position and I bolted everything back in.

I have downloaded a noise measuring app onto my phone to test if there was any difference.

Before installation, I measured the exhaust sound to be 82dB at idle and about 88dB at around 4000rpm. After installation, she was making 78dB at idle and 82dB at 4000rpm. That was quite a nice improvement. The exhaust is still a little louder than what my K1 was making with her stock system, but that obnoxious roar was gone when I revved up the engine.

Flying Under the Radar

Risa is now quieter and I have “tested” it twice so far. I went passed enforcement officers who were parked at the side of the road twice and both times, neither even looked in my direction as I went by. That was good news. I don’t know if the dB killer became a HP killer instead, but as far as my butt tells me, the engine still runs well and has more than adequate power to scare me, so that is probably a good thing. Lol…

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