First, let me thank those that participate in this forum. I have found it to be an valuable resource.
My problem: I have a 1981 Yamaha QT50. I has only 1200 miles on the odometer, but has sat unused for the last ten years. In getting it operational, I have cleaned the carb (twice), added a fuel filter between the tank and the carb, replaced the spark plug and air cleaner element, drained and replaced the gas and oil.
It now starts and idles OK. However, when running at speed, say at 15 mph, it wll hold that speed for 15-20 seconds then start to buck, miss and backfire, often dying. Sometimes on restarting, a big backfire will occur. I must add that before I found this site and Fred's tutorial, I was "playing around" trying to get it going and may have changed some setting. Any suggestions?
A second minor problem is that the brake light does not work, despite a new bulb.