Downgrade spring? 7.4V lipo (if not an 11.1)? More powerful motor (easy drop in replacement but ideal would be to work on gears first)? Torque up gears?
PS: If you want a good motor for the price the Guarder Infinite torques are really good IMO, not too expensive and pretty good performance.
ಠ_ಠLess QQ more Pew Pew
READY TO >> RACE