I put a Noss Machine high performance head in my 2001 banshee and it wont stop leaking around the 4 center bolts. I called Noss and they sent me a set of brass washers and acorn nut but it still leaked. I called Noss again and had them send me a new O-ring set. I completely cleaned and inspected everything and even put RTV silicone on the bolt heads but cant get it to work. I finally had the stock head shaved and put it back on. I am going to sell the NOSS hesd on E-bay and try to recoup some of the money. I love how this product looked and ran but it was just too much of a headache! Even the people at NOSS didnt know what to think. I do appreciate all the help they gave me though.