I picked up a 1993 130hp Yamaha 2-stroke. The compression numbers are pretty good, 125-130lbs in each hole. Starts and idles nice but will kill sometimes just before planning off. Got a leak down done and the #4 cylinder was at 21%. So I pulled the head and the #4 hole has a rust spot on the top of the cylinder wall. Is it possible to remove the rust and smooth the wall without doing a complete tear down and rebuild?