I have a Vespa ciao around the mid 1970's. It has always worked and there has never been any problems. Last time it ran it started fine but when i took off the speed slowly decreased until i finally stopped. I have replaced the spark plug, cleaned the filter, cleaned the carburator, cleaned the muffler, i have compression, there is gas in it and the electricity is fine. so if i you know whats wrong with it help me out!