I've been following the sprocket issue. My Dad worked for Equipment Services in Anchorage when they were the dealers and bought a new ST4. If I remember correctly they were re-facing the sprockets back then. Has anyone tried this approach? I have a friend here in Homer that owns a Propeller shop and they re-build boat propellers all day long. They weld new material on the edges and grind off the excess. There's a specialty welding rod site that might have the correct bronze. I'll check it out.