Freshen up your exhaust and engine bay with a new exhaust coupler.  These are cut from the same blue and orange material used by manufacturers such as Factory Pipe. Don't let an old crusty exhaust coupler take you out of the race. 
2.25" fits: 650SX/X2  head pipe 
2.75" fits: 650/701/750 Coffman's head pipe
4" fits: Factory Pipes (B pipe, Half Pipe, 750sx/800sxr wet pipe),  650sx/X2 chamber (tight fit)
 
5" fits: Most Coffman's and PJS chambers except 550