WildBill, sometimes a foreign matter will find its way into the spraybar, and causes many problems. Try the solution Ken has described above, and if it fixes your problem , then moisture was the enemy. If problem persists, the remove the needle valve, and also remove the spraybar fron the engine. Using your fuel pump, connect it to the inside end of the spraybar and give a short burst of fuel through the bar. This then should flush out any matter that has collected in the bar. Refit the bar to the engine and replace the needle. Do this at home in a clean enviroment , less chance of adding more particles into the system. Remember when fitting the spraybar to the engine , the venture in the bar should be facing down into the carby body. Hope you get your problem fixed and continue to enjoy many happy hours of flying
Bill