The engine on the Toro 6.5 HP lawn mower has a governor that controls the speed of the engine. The purpose of a governor is to control the engine speed. Left on its own, the engine potentially runs too fast, and it could literally start breaking apart. The governor prevents this from happening by limiting how fast the motor can operate. In order to make your engine run faster, you must adjust the governor. When adjusting the governor, it is important to understand that a small adjustment can make a huge difference in the engine speed. The governor works the same way on most small engines, regardless of brand.
Remove the air cleaner from the top of the engine using a socket and ratchet. The air cleaner is on top of the engine, off to the side. Some mowers may have wing nuts instead of hex nuts.
Look for a vertical arm with springs attached to it. This is the governor.
Bend the arm slightly the left using the needle-nose pliers. Think in millimeters rather than inches when you make the adjustment. A tiny movement can mean a significant speed change when adjusting the governor.
Replace the air cleaner on the engine and tighten the retaining nuts. Start the engine. If you adjusted the governor too much, repeat the process, except bend the vertical arm to the right a little. You might notice the difference in the engine speed when you start it. If it sounds like it is running too fast, you need to adjust it back.