Dirt in the carb is not neccesarily the end of an engine. The most important thing is to NOT turn the crankshaft over until you get the engine completely cleaned out. I use some old fuel and a toothbrush to clean engines. Clean all the dirt off the outside, and then take the spinner, prop, muffler, glowplug, carb, and the backplate off. Squirt fuel all through the crankcase until it's clean. Then try carefully turning the crankshaft. If it turns smoothly then the engine should run OK once it's reassembled. If the crankshaft wobbles or grinds, then the crankshaft is bent and/or the bearings are bad. Then you have to decide if its worth messing with, or just a 'parts' engine.

Dry the parts off with a clean towel, and then put about a teaspoon of after-run oil or transmisson fluid in the crankcase. Work it in good; make sure the entire inside is oiled, especially the bearings. Put the engine back together, making sure all the bolts are tight. Mount it on a test stand and see if it will fire up.
Good Luck!