When is the pull start hard to pull? It may be, like said above, that it the settings are too rich and flooding the engine, making it hard to pull. If it's from trying to start it cold, heat up the engine with a heat gun or hair dryer or loosen up the glow plug. This should release some of the compression and make it easier to start. If you are doing the glow plug method, make sure to tighten the glow plug after it starts.
The engine going without power (Throttle?) is from either the transmitter settings or the idle settings. Make sure that the throttle trim settings are set to neutral. If it still goes, your idle settings are off. Adjust the idle needle so that when the car is on the ground it will not go.
