The intake components appear to be the most restrictive portion of the unit's potential.
The carb is a China made WT675. The "20" in the casting throat indicates a venturi size of .3125" (20/64).
If you look in the attached pics the venturi is seriously obstructed by the butterfly shaft as well as the screw holding the butterfly to the shaft.
Additionally this carb only has a low end needle. Can anyone explain how a single needle carb should be tuned?
As well if anyone can suggest an alternate carb I'd like to hear suggestions. I'm wondering if a WT644 would be too large for a gas / glow conversion of 25cc?