Hello, the reason why the choke is required is the fuel/air mixture is not proper. Either due to carb being out of adjusted, or gum/varnish build up in the float bowl. You are correct it takes one of two special tools either a "pac-man" or a "D" adjustment two, aptly named for their shape. Both can be easily had on amazon.com. Has this trimmer sat for any extended period of time? or has it sat with the engine toward the ground?