These mowers have dampers that are located under the seat and dampen the shock movement of the handle. When these go bad the handles may get "jumpy" or "jerky" feeling. The part number for this is 285025 for the right side handle and 285030 for the left side handle. Another point is that system is a high pressure system using Gemini transmission. Paired with a high pressure system and bad dampers it will may seem like it will throw out of the seat! Hope that helps some.