I have seen some YS 45s on that auction site and other places with mufflers. They were even advertised as the muffler for the engine. I don't know where you can get one now. I have a YS 61 that I found a Mecoa muffler that needed just a bit of filing in the mount holes to fit. I'm sure there may be a similar muffler for the YS 45. If you do find a source for YS 45 mufflers, please post it here for the rest of us. Thanks