I have done this several of these, centre the pot. I do by connecting it to a receiver
, put the trims to, centre on the Rx switch
on and move the pot so that the motor
stops on the servo
, then put some super glue on the pot and leave for short time, replace the small gears, the last gear has a small tag on the lower part of he gear, snip it off, and open up the hole in the gear slightly, replace the gear and the top gear. You can then use a spare channel
on the rx to adjust the speed on the servo
in both forward & reverse. if you have any trouble go on mayhem under the black arts section and there is a vid on there.