Was this packing bad ?
OK, so it may seem that the weakened packing from 167hrs might have not been able to withstand a newly rebuilt motor with that much compression. Think about this, when you installed the new 0hrs aftermarket exhaust the engine already had roughly 70 hrs on it so compression was not at its prime, then 167 hrs later a worn out packing couldn't with stand the compression from the fresh engine. Just my thoughts.It is a Rocket exhaust and it was the original packing with 167hrs on the packing on a 07 kxf 250 with 248 hrs on the bike. 1 valve job and piston at 120hrs and a rebuild at 240hrs