I drained my gas tank again today, flushed the tank, cleaned both fuel filters, cleaned all the carb's channels and jet, and this eliminated a sputtering which I was tempted to blame on the exhaust system plugging again. Doing these little chores one at a time instead of grouping them in one big day is slowly teaching me what effects are caused by what defects. I guess I grouped it a bit, by cleaning and reoiling the air cleaner, but it wasn't dirty enough to affect performance. I just wanted it fresh for my summer's tripping.