These are the key things I have noticed your temp is low, spitting of fuel which can be a good thing at this point your problem might be hydraulic lock, this happens when unburned fuel lays on top of the piston and the piston is on its way up blocking the ports, the unburned fuel has no where to go thus when you try to start the piston comes up and the fuel has no where to go and this is where engine damage can occur such as bent connecting rod, wrist pin or crankshaft which could explain the back firing because it would be out of time, always make sure before you try to restart your engine that your piston is at the bottom of the stroke. I would take my engine apart and check the connecting rod the bearings then wrist pin and crank also check for debris. If it is what I have seen the connecting rod will go first and your looking at about $33. If your engine is new and tight your going to have problems getting the rod off the crank so be patient it may take a while and remember if you scratch the rod bearing it is toast. While your at it its a good time to check your bearings, you may consider putting in one way bearings. Good luck and Happy RC ing. If I can be of any help.


Holly