Seems impossible that if the valves are adjusted correctly and the engine runs smother that it would have a loss of power. How did you determine that there is a loss in power? The only way to really tell is to see how fast it goes up a long hillbefore and after but the conditions must be exactly the same: wind speed and direction, temperature, and barometric pressure. If it doesn't seem to have enough power on a hill, this is a symptom of a plugged fuel filter.

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