It is not right, but it is a fact that if you have an Evolution with about 20,000 miles on it, you have a base gasket leak!The factory has tried to remedy this problem with at least four different styles of cylinder studs to no avail. Simply tap the cylinder in the top end oil drank back hole with the supplied aluminum tap and install the Pig Tail with about one inch left protruding to be inserted into the crankcase. This method totally eliminates top end drain back oil from even touching the base gasket. For best results use with metal base gaskets. Pig Tails can be easily removed for cylinder service and are designed for OEM size cylinders (not intended for big bore cylinders). Instructions included. Fits all Big Twin and Sportster Evolution. Manufacturer