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Silencers

Bob Gilpatrick

One of the issues I have been dealing with ever since I put the Supersports on the road has been exhaust noise. The first silencers I installed, I have to admit, were chosen as much for looks as for function, that is, to muffle the exhaust noise. The first silencers were "Dunstall" types obtained through ebay. They were not any kind of OEM types so they did not meet USA minimum standards of maximum 80 dba. They worked well enough with the 2CV engine but were still loud and annoying.

When I made the engine conversion to a 2007 Moto Guzzi Brevaie 750 I kept the same silencers but with the greater power of the Moto Guzzi engine they made more noise which became annoying and caused me to look for another type of silencer.

I saw an advertisement for the "Super Trapp" type of silencer. It seemed to have many advantages, including very small size and light weight enough to be clamped to the end of the exhaust pipe without any other support. In fact I considered placing them on short stacks in the front and eliminating the long pipe to the rear of the car. The Super Trapp is not a silencer at all. I'm not sure they serve any purpose at all except to build up some back pressure for the engine to breathe properly. They are LOUD and have a snarl which will drive you out of the cockpit unless you are racing. And, where I had them mounted the exhaust fumes in the cockpit were overwhelming.

My third attempt was to purchase and install a MAC silencer which again looked great but was again LOUD!!!. I finally came to the realization that "after market" silencers, especially the less expensive ones, are for MAKING NOISE for those who want to make a statement with their internal combustion vehicles. They do not in any way meet the current USA 80dba maximum noise limits In fact, those silencers come with a caution that use of the after-market silencers may be a violation of Federal noise standards. Really! The MAC silencers were on the car for such a short time I didn't even take a picture of them.

The noise of those after-market silencers was annoying and tiring for me and my sometimes passenger and embarrassing when I was in company of the car clubs. So I decided to look at OEM silencers which would meet the 80 dba limit. If the silencers comply with the Federal standards they have a statement stamped in the body of the silencers stating that they comply. Of course we're are talking about motorcycle silencers. I quickly found out that "new" OEM silencers are outrageously expensive so I ruled new silencers out. Also, since I am using 1½" OD exhaust pipes, there is a very limited selection of silencers with that small an inlet pipe. My search quickly narrowed down to "used" OEM silencers which would fit my 1½" exhaust pipes. My good fortune! A few doors away from my shop is a motorcycle salvage dealer. I asked his advice and he said that the 1990s era Kawasaki Ninja 250 motorcycle silencers may be just what I would need. He went on to explain that the first thing that people that buy Japanese motorcycles want is silencers that give more power and noise so they take off their OEM "quiet" silencers and buy the after-market ones from him. He said there is a very small market for the OEM silencers he takes off from those motorcycles and literally hauls them to the dump monthly. The Ninja 250 OEM silencers from the 1990s are getting hard to find but he was able to get a set from deep in his warehouse.

Those silencers have a 1 3/8" OD inlet and the inlet pipes are not straight. I had to expand slightly the inside diameter of the ends of my existing 1½" exhaust pipes so the silencer inlet pipe would fit inside the end of the exhaust pipe instead of slipping-on over the outside. I also had to bend the inlet pipe of the left side silencer so it would fit in my existing support bracket. After securing and clamping everything I was able to start the engine and hear the most beautiful exhaust note. The cost, other than my labor? A case of beer. Cheap enough.I will shortly post a short video of the final results on my blog, pembletondaytona.blogspot.com. Take a look. In the next couple of days I will disassemble both silencers for cleanup and painting. I have yet to decide on a color for the silencers. I guess black or silver.


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