Update to previous question. Now, no matter whether the mandrel guards are on or off, the engine dies as soon as we try to engage the mower blades. We put the old belt back on and the same thing happens. The engine runs great until we engage the mower blades. We've tried adjusting the spring tension on the belt; makes no difference. Any ideas?

Hi,
This a safety switch problem, Check wires the deck switch or seat switch or both.
Peace,
Clarke