On all my older Tigres I drilled out muffler bolt threaded engine cases so I could use straight thur bolts. Don't even think about using muffler gaskets, just a little RTV. The economy mufflers are light and great and I do like the bullet Italian swing mufflers, but they are heavy two. A tower 46 muffler and a little filing to make muffler holes wider are the best fix. Don't forget the dab of RTV .