Dont drill. Get a grinding disk and grind about 3/16´s off eng of muffler. It will expose the baffle which made into the end. It is rolled. It cuts the small opening off and exposes the baffle which you reach in there and pull out the baffle out. I done it yesterday and it is the best sound you can get. Plus the opening is full size of the pipe. Jets 118, get a 3/64 drill bit. Stock air filter and stock pilot jets, 1 1/2 turn out. Runs great and gets 50 mph. You could probably get by without jets, just check your plug for the nice tan or light brown color. Thanks