On my Snapper 52" hydro walk behind mower, the Operator Presence Control isn't working right. To start the mower (it's recoil only) I have to hold the OPC on with one hand while I pull start it with the other hand. If I let go, it stalls the mower whether the blades are engaged or not. What should I be looking at? I'm not the most mechanical guy, so speak slow!