Small Engines (Lawn Mowers, etc.): 18.5 B&S running problem, fuel filter, snail

Question
My Murray 18.5hp 46" cut rider will start right up and only idle at best.It will not run high enough to mow or move the mower fast than snail speed.Gas is free of water and throttle inkage looks fine.Any ideas as i have looked in the carb but find no sponge? i was told should be there?
Thanks for any help..

Answer
Is the throttle working correctly?  When you place the throttle in the fast position, is there tension on the governor spring?  I have found springs that came loose from the governor.

Have you cleaned the carb, replaced the air and fuel filter?
Let me know.
Eric