If you're meaning the end of the header, the widest across the heat shield is 2 3/16 " and the narrowest at the outlet is 1 3/4 " .

The part about the carb exhaust drops is confusing.

2005 Model . Two Fast Eddy stickers , a bell and a clock . She's Lola . She tinkles and keeps time . http://s649.photobucket.com/albums/uu211/britbike05/