This Kit replaces vital components in the BST40 Carburetor including new o-rings, gaskets, jets, needle, mixture screw, float bowl screws, float valve needle and seat (needle jet and other pressed in jets are not included in kit) to return the stock Mikuni BST40 Carburetor to like-new operation. As a bonus we have included Viton o-rings for the float assembly and 4 stainless steel allen screws.