RE: Throttle Servo Hook-up
I don't know why no one has responded to your post. This forum used to be full of knowledgable blokes willing to help....
You need a little pre-load on the return spring but not a lot, the servo will buzz if you overdo it as it fights to keep neutral.
Can you adjust the end points on your radio? Mine are set so there is more servo travel for the brake than the throttle.