[twobore]

My G1 engine had an ear splitting exhaust noise. I took a length of vinyl tubing and, using it like a stethoscope, listened around all the exhaust joints, muffler seams, etc I could reach. When I stuck it under the Exhaust flange between the engine and muffler (the exhaust pipe that contains the butterfly valve - Yamaha parts list’s call this a Nut, Ring) - I not only found the source of my noisy exhaust but got hit with a blast of air from the hose to confirm it. I removed this part and discovered a sheet metal cup that is a press fit onto a cast stud on the exhaust flange (see arrow in Pic 1). The cup had vibrated loose and was allowing significant exhaust leakage , causing my Harley like exhaust roar. Inside the exhaust flange there is a circlip at the bottom of the shaft that rides on the seal held in place by the sheet metal cup (it’s on top of the washer in Pic 2 - I added the bottom, larger washer). Unfortunately the circlip is smaller than the inner diameter of the shaft so when the cup loosened, it allowed the whole works (cup, seal, circlip) to drop until the butterfly valve bottomed out allowing massive exhaust leakage.

To solve this problem, I added the larger washer inside with the circlip riding on top of it (Pic 2). Now the assembly can’t drop down even if the cup should loosen. But to make sure the cup does’nt drop, I added the two small washers at the bottom of the shaft (Pic 1 & 2).

I kept trying different washer combinations until everything fit snuggly without binding. I also replaced the two original M3 x .5 phillips head screws with stainless steel cap head (allen style) screws and locktited them in place.

This solution cut my exhaust noise in half. I’m a much happier camper.