In the process of restoring my B 112. It has a 16 HP B&S. All my other units have a standard 1 1/4 inch threaded pipe for exhaust. This one has a 1 1/2 inch OD threaded piece. Connected to it is a tubing with a 2 bolt exhaust flange. 1 1/4 inch pipe is not 1 1/2 inch OD. What is this and where can I get it? Confused.