Recently picked up a used white riding mower mfg’d by MTD. The engine is a Tecumseh model OV490EA. The machine had not been run since last season. Overall the tractor appears to be in pretty good shape. Not knowing the history, I drained the gas, changed the fuel filter, drained the carb bowl, replaced and filled the gas tank with fresh gas. Also change the engine oil and filter and cleaned the air filter. I Had to prime the carburetor with a little gas to get it to fire. It started and ran great. The next time I went to use it, it would not start. Again I primed the carb and it fired right up and again ran great. This process continues. What do I need to repair so that I can start the engine without having to prime it with Raw gas down her throat?