You should only have to replace if the throttle shaft holes in the body are worn out. You can replace every part in this carb. There was a AD on some Marvel floats and venturis. And fuel pressure is always nice to have. You may have varnish or other contamination in the carb body. It should be soaked in a dipping cleaner such as "TYME" for the correct amount of...time. Poor throttle response is a symptom of a bad accelerator pump, and leaning under load indicates low fuel pressure or low fuel level in the bowl. I rebuilt my MA-5, it isn't hard. dale stephen langford wrote: > FlyBaby > > Hello again, > I have cranked and run my engine. > Have about 20 minutes on it. > It is an O-200 with a Marvel MA-3SPA # 10-4894