There is a place where you can send your head to have it repaired . They put a heli coil in to repair the threads . This is something I am sure you must know but I will mention it anyway . Are you charging your transmitter and is it holding the charge ? You have two sets of batteries to look after . One set for your aircraft and one set inside your transmitter . They both must be charged seperatly . If you are trying to start your engins with the old fuel tanks you should replace everything . New tank,new fuel lines ,the works . The old stuff is rotten by now . Start over fresh . Four stroke engines have valves that get sticky and need to be clean and free working . A good soak in glow fuel should help . I would only dismantle as a last resort . You could take the carb off but don't get into takeing the valves apart if you can help it . You need to be careful and make sure things go back together the same way that they came apart . The little springs and retainers can easily go flying .