If you are using a 2 stroke in-frame motor without a centrifugal clutch the sounds that you hear are probably the manual clutch, chain/sprocket. Even with the clutch disengaged and if the rear wheel is spinning there are parts moving that can make strange noises. If you're certain there is no interference with rotating parts and your chain tension and alignment is right, I wouldn't worry about the sounds. Just keep an eye on things and make sure there is nothing external rubbing.
Tom

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