I picked up a Cycle-X 4-2-1 exhaust system in the spring for a price I could not refuse. The previous owner wasn't happy with the visual styling or the sound output of the exhaust system on his cb750F.
While he was happy with the performance and the ground clearance, he preferred the sound of his old kerker exhaust to the new Cycle-X exhaust which he found too buzzy. He listed the pipes for sale on the 1100f forum but there were no takers after his slightly negative review of the pipes. Then he listed them on ebay and I watched the auction close with no bidders.
Still recovering from my family's financial mess from the winter of 2009, I was determined not to be drawn out from the shadows to buy the pipes until he lowered the price some more and relisted. After receiving only 1 bid for the whole week, I decided to put in a bid during the last hour and step away from the auction feeling confident that I would not win and feeling even better that I had atleast tried to buy them at the terrific price point since I was certain the first bidder would come back and outbid me. Fate thought differently and I won the auction.
My first impression on starting the bike was that at idle it was a fair amount louder than my stock 4-4 exhaust system. I discovered the "buzz" the original owner complained about at around 4-5k rpm. Uninitiated friends and relatives said my bike sounded like there was something wrong with it becuase the buzz had a certain ringing tone to it as I rode away. I knew I would be changing something with the muffler at some point but decided to just experience the exhaust as Cycle-X intended. My seat of the pants experience was that the bike sounded angrier but not sure what happened to hyperspace mode I experienced with the original exhaust. I either got used to the speed or the bike is now slower.... I'm not sure.
This is the baffle as manufactured by Mac (Cycle-X outsources the manufacture of these pipes to Mac). Quality appears decent. Welds are not beautiful, but the metal feels thick enough to be substantial without being a boat anchor.
In my first attempt to quiet the pipes down, I welded some stainless steel angle pieces onto the baffle with the intention of changing the angles of the exhaust flow to increase the chance of some sound cancellation and this worked at idle but the slightly quieter exhaust did not attenuate the buzzy sound at 4K+ rpm at all.
My 2nd attempt at decreasing the sound level involved adding some course stainless steel pot scrubbers around each new angle deflector as well as adding a straight through baffle with some more SS pot scrubbers to absorb some of the higher frequencies much like adding baffle to an enclosed speaker.
This resulted in lowering the exhaust note to a more deep tone as well as decreasing the overall volume of the idle sound to the point where I can hear the engine (valve clatter?) in addition to the exhaust. While there was still some buzz at 4K RPM, this seems to have gone away after going for a short ride. There has been no change to the performance and I'm now quite happy with the modifications to the baffle to quiet it down a bit.
Here's the final design:
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