I just want everyone to know about this slip on exhaust. My 2000 xr 600 started on the first kick for the very first time. I put on the larger tip opening that came with the bike and it opened her right up. More power everwhere. The sound is awe inspiring and the increase is definately noticeable. The best thing is how easy she is to start now. I am not exagerating. If anyone has a hard time starting their big bore 4 stroke, try one of these. Easy to install, great design, perfect fit and great overall performance. I still need to dial in the jetting but its not too bad as is. I just bought a pumper carb from Edelbrock (Barnums) and can't wait. Just wanted to share this with you all.