I started a post about the head pipe cylinder junction gasket. It protrudes into the exhaust port ,I temporarily used a O-RING ,just to test. You mentioned 8 gauge soft copper wire which by the way is a excellent idea. I went to Lowes they only had 6 and 4 gauge,I purchased the 6 gauge and made a gasket. Long story short the thickness of the 6 gauge just cleared the exhaust port,I mean just cleared it,too close for my comfort. I went to Home Depot and purchased 8 gauge made a gasket and it sits in the exhaust port with perfect clearance. How you pulled 8 gauge out of the air simply amazes me:thumbsup: Just like a 2 stroke a 4 stroke needs to expel the exhaust gases efficiently.With a gasket that does not hinder the exhaust gases the 450 pulls longer with definetly more over-rev felt.The motor definetly feels thicker. Hopefully the copper does not expand from use,like the KX's in the past did. The exhaust gasket on the KX's 2 stroke use to get really flat and thin with time. The stock YZ 450 uses copper on both ends inbetween the copper is some type of wire like steel wool. I am just running the copper gasket I made,we will see if it holds up. If IT LAST A GOOD 10 RIDES I WILL BE HAPPY,I PAID 1.80 FOR 2 FT OF IT. Which will get you about 5 gaskets. gray again good call on the 8 gauge.