Back in 2012, I added some fiberglass wrapping to the spark arrestor to quiet the sound level some. On my 2010, it seemed to work pretty well, with a significant effect on the noise. It did not seem to affect the carb tuning much, although above 8,000 it seemed to run quite rich with the stock jet. I lived with that for 6 years, only changing to a 122 above 9,000. Average altitude was 5,000 to 8,500 feet. It ran fine at sea level with that set up.
Fast forward to the (second) new 2018: After adding as much fiberglass as I could get in there and some break-in, I noticed significant bogging in 5th gear above 50 mph. I continued to be conservative about WOT runs downhill, not exceeding a minute or so. Now, at 850 miles, I decided to figure this out. First, I took the air cleaner off and ran the same 2 mile stretch slightly uphill and then downhill. The bogging disappeared. Then I removed all the fiberglass and put the filter back on (back to stock) and did it again. Bogging was much less but still there. After some discussion with my local tech I decided to stick a 122 jet in. So I re-wrapped the spark arrestor with as much fiberglass strands as I could fit and went out for a WOT cut on the same stretch. I was worried about the possibility of being way too lean, but the plug showed nearly perfect color. There was only a hint of mild bogging after a minute of WOT. The bike easily accelerated up to 60 mph downhill (13 tooth front sprocket).
I have no idea why the 2010 went for 7 years on a stock 126 jet with a packed muffler and the 2018 needed a 122 under the same conditions. I have yet to get the new set-up over 6,500 feet, but it didn't bog up there, either.
So for anyone who tried the muffler wrap and found the bike running too rich, I apologize. If you want to significantly quiet the exhaust note by adding fiberglass you will need to go down one or two sizes on the main jet. My TW now sounds like a moped unless under acceleration or up a steep hill and has plenty of power. I will have to change back to the stock jet when I go down to Death Valley or Phoenix.
Fast forward to the (second) new 2018: After adding as much fiberglass as I could get in there and some break-in, I noticed significant bogging in 5th gear above 50 mph. I continued to be conservative about WOT runs downhill, not exceeding a minute or so. Now, at 850 miles, I decided to figure this out. First, I took the air cleaner off and ran the same 2 mile stretch slightly uphill and then downhill. The bogging disappeared. Then I removed all the fiberglass and put the filter back on (back to stock) and did it again. Bogging was much less but still there. After some discussion with my local tech I decided to stick a 122 jet in. So I re-wrapped the spark arrestor with as much fiberglass strands as I could fit and went out for a WOT cut on the same stretch. I was worried about the possibility of being way too lean, but the plug showed nearly perfect color. There was only a hint of mild bogging after a minute of WOT. The bike easily accelerated up to 60 mph downhill (13 tooth front sprocket).
I have no idea why the 2010 went for 7 years on a stock 126 jet with a packed muffler and the 2018 needed a 122 under the same conditions. I have yet to get the new set-up over 6,500 feet, but it didn't bog up there, either.
So for anyone who tried the muffler wrap and found the bike running too rich, I apologize. If you want to significantly quiet the exhaust note by adding fiberglass you will need to go down one or two sizes on the main jet. My TW now sounds like a moped unless under acceleration or up a steep hill and has plenty of power. I will have to change back to the stock jet when I go down to Death Valley or Phoenix.