Re: Quieter muffler?
The 'after-muffler' idea works well. Another option than brazing or welding is to go the the hardware plumbing section, get a brass compression fitting that will snug fit over the exit tube on the stock muffler, step up from there to a 3/4 pipe thread, put on a 45 degree pipe elbow, and screw in a 3/4 pipe thread generic Briggs-Stratton muffler. Use a small piece of metal or plumbers tape (strap) to support the after-muffler to the bottom of the bike frame to relieve the stress on the header pipe up at the engine head. Very neighbor friendly!
The idea of drilling holes in the after muffler to let oil drain is a good one! And being fitted onto a threaded fitting, easy to take off and clean if needed.