Find out why it's stalling. For hard starting, the first thing to check is the carb. Some of these carbs. developed bad o-rings that tend to leak and let air in (and fuel out!). If it's going lean as the engine is heating up and stalls, the fuel will have a hard time getting to the carb until the engine is cooled down again. Kyosho sells the repair kit that has the o-rings for the main needle and low speed adjustment.
Also, bad fuel lines with even just a pinhole will cause these problems.