Sad, little man......First things first.
If your throttle will not work properly.....it should be the first thing you attend to so your rig is not going "out of control" on start up.
Your going to be the one to determine why it's not working properly.....so you'll need to look at what is causing it to behave in the manner that it is. That being said....
1. How is the linkage set up from the servo to the carburetor? Is it sticking / binding? If so...you'll need to fix that.
2. With the linkage removed from the carb....can you move the barrel freely with the air filter off and see it moving freely? Is it opening all the way....and closing to around 1mm? If not....then you'll have to look for reasons why.
3. Starting an engine.....any engine from a cold condition and going to a high RMP is not good on them. Once started.....letting the engine come up to an operating temperature is the best method before laying on the throttle. Since your engine is not working properly....I would be working to resolve whatever is causing it to start wide open upon start up.....before you damage it.
4. With the radio gear turned on....and all settings are set at a neutral position.....with air filter off of the carb....look into the carb to see how far it's opened up. Is it at or around 1mm opened? If not....then you have some adjusting to do to the throttle linkage....check it out. Something is not allowing the carb to work properly.
5. You mentioned that you lost a screw? What screw did you loose? Has it been replaced? Maybe you should wait until you have the new one in it's place?
6. You can use the trim settings on your radio to help open the carb barrel far enough to get the engine started without needing two people. Just adjust the throttle trim to open the barrel on the carb so you can get it started.....once started....move the rim back to where it was.
Most of all....be safe! If it's taking off out of control....no telling what's going to happen. Reaction time can be split second and I know you don't want to hurt your rig or someone watching you.
Good Luck!
