I always use Permatex Hi-Temp RTV Silicone for all my pipes, sled, dirtbike and quads. I just put some on the head pipe end where it meets the stinger end, then shove the stingers on. Then i lay a nice wide bead around the joints, let it sit for just a lil bit. Then i clamp my clamps on and they never leak or drip ever, good stuff.
http://www.permatex.com/products/Automotive/automotive_gasketing/gasket_sealants/Permatex_Hi-Temp_RTV_Silicone_Gasket_Sealant.htm