Ewww. First thing after a dirt bath I DO NOT MOVE THE THROTTLE OR PROP SHAFT and squirt loads of WD-40 into the engine held with the carb barrel low. About 15 blasts with a pause in between to allow the dirt to flush out. If you are careful a full dissassembly and cleaning is probably called for. If not you can't go far wrong sending it to the service center and asking for an estimate before work is performed.

When you run an engine with dirt it scratches the cylinder wall and/or piston and you lose compression. The results are much like you describe. No idle, poor transition, low top end, flame-outs. A really hard impact can dent the sleeve with the piston and give similar problems.

If it is in warranty you might be able to send it back for a new sleeve & piston (they did with no charge for my Thunder Tiger .46 even though I held and took full responsibility for the crash).