I just bought an XR's Only exhaust for my XL600R and it is a bit larger than the stock header. I just had to patch my old rusted pipe that connects the muffler and header with Tiger Patch. You put a piece of tin over the hole, wrap it with this stuff, run the engine for 20 mins., it melts down and then hardens. Since the gap is so wide between the new muffler and header, I plan to cut the old tailpipe section to put over the stock header, wrap it with some Tiger Patch, then wrap it with some tin, still more patch over that, then mount the exhaust and clamp it. Does this sound stupid to you? Anyone have any experience with this?