We have a weird starting problem. Sometimes will start. We have spark, timing is on and good compression. If we spray starting fluid or carb cleaner in carb, it will not start. But if we blow air down the carb while cranking, it will start right up and run as long as there is some throttle applied, but will dies when throttle is released and will not start until air is blown in carb again. If anyone has any ideas or suggestion, please let me know. Thanks