Yes, you should be worried. The shaking and vibration noise are serious warning signs. The immediate cause is typically loose or damaged blade bolts. A secondary cause is damaged, bent, or unbalanced blades.
- First, turn the fuel valve off and disconnect the spark plug cap for safety.
- Tilt the mower onto its right side.
- Inspect the two blade bolts for damage or looseness. They must be torqued to 36–43 ft-lb.
- Inspect both blades for bends, cracks, or excessive wear. Look at the trailing edge shape to check for imbalance.
If the bolts are loose, retorque them with a torque wrench. If a blade is bent, take the mower to an authorized Honda dealer for inspection. Do not operate the mower with a damaged blade; it can break and become a dangerous projectile.
Always use only Honda Genuine blade bolts and the special washers designed for them.