I would be tempted topull the intake side apart so I could closely inspect the reed valves. Factory has a tolerance of how large of air gap may be between the valve and seat. A small gap will allow a certain amount of crankcase pressure to bleed back into the intake, reducing power at low speeds. Once the motor gets closer and into its 'power band' the reeds are no longer required as there isn't time for much leakage.
New reeds or aftermarket reeds should make a world of difference. But I seriously recommend inspection before ordering anything. I have been wrong before.
Don't even THINK ofo turning reeds over. The metal will soon break and allow sharp pieces into the cyl doing terrible damage.
