Very nice running motor, and it will probably run a bit faster as it gets run in. it might be worth experimenting with flywheels, i'd strat with one about the same weight, but slightly larger diameter, with the weight consentrated at the rim, and spokes or holesbetween the rim and the hub, weight in this part is not helping the motor too much, just adding weight on the bearings.
The above is just my idea of model engines, i build then fiddle around to see if I can extract a milli watt more power.
Ian S C