Small Engine Troubleshooting Problems? Ask a Mechanic Now.
Drive is with a belt from engine to the transmission, is the belt tight? Has belt ever been replaced? There is no adjustment on the belt, it has a spring tensioner that should keep it tight. I suggest trying a new drive belt. See the link above.
There is nothing but a basic linkage adjustment , as there is no clutch, other than the pedal you push! The (clutch) is the belt!
I think that will do it!