Directed by Murphy. The remedies are fairly simple and I had not planned to discuss them. The engine-noise in a Bullet originates from one or more of the following sources. They are classified into three categeories. This is as easy to remedy as to check.
Few minutes job each.
Only then go on to other possibilities. Make sure both the ends are well tightened. Or you will have buzz-iness in the handlebars, and pinking sound on acceleration. A BANG on deceleration means an exhaust-leak, and the cause of that may be the improper fitting of the exhaust bend. Test it by striking the muffler with a piece of rubber-hose or with your finger.