Thanks guys. This helps me out a lot. Also forgot to ask what would cause a malfunction similar to a clutch going out ( not sure if these have a clutch or not. )
disclaimer this is not my picture, i found it on google for depiction (my engines are in vehicles atm so harder to show this)
nitro engines that we use, use what is called a centrifugal clutch, the shoes sit on pegs (yellow arrow below) that are pressed into a flywheel (red arrow below)
as the flywheel spins the shoes, the centrifugal force overcomes the tension of the spring (green arrow below)
side note: some clutch assemblies use a single spring that wraps around the shoes as below, other types use a single spring per shoe
as the shoes are forced out, they make contact with what is called the clutchbell (red arrow on the left above) and that is what moves the car.
if the clutch spring is worn, or bearings are locking up, the engine will not be able to rotate correctly and will have too much drag on it, and as the engine is in low RPM range and does not have enough power to overcome, the engine will stall easily if the tires are on the ground, or if the truck is suspended and tires are spinning, as soon as the tires meet resistance, the engine will stall.
make sure when trying to diagnose this that the engine is in fact at low rpm as a too high idle will cause the same issue but will not be as susceptible to dying, as it is doing what it should be just other settings are wrong making it act like it is an error in the clutch assembly.
as far as what the issue is, if its dying and it wont sit in place at idle, it would be the clutch springs being too weak and or broken, or the clutchbell bearings being bad and locking up.
if it is running but you can't get the vehicle to move (this is the case if the clutchbell is not spinning). it can either be the clutch shoes are too worn, or your flywheel has loosened and is spinning freely on the crankshaft.
if the clutchbell is spinning, and its further down the line it could be a number of things like Olds said.
hope that helps!