Losing my mind, I've tried everything. This in on my JD 455 with 600hrs. Engine starts fine but when I increase the throttle the governor goes bananas and the engine idles faster then slower then faster then slower, etc. It then blows white (blue) smoke. At first I thought I blew a head gasket and was leaking/burning coolant. Bad assumption, tore the engine down replaced and cleaned and still has same problem. Fuel filter looks new, compression is above spec. Smoke may be caused be bad reed valve, I do see an accumulation from the breather line feeding the carb. Why the erratic operation? I'm clueless.