I am having a problem with a Homelite string trimmer, model
Z625C.

It starts without difficulty, but as soon as I touch the
throttle, the engine dies. It will restart again, but dies again with
use of the throttle.

I believe that the fix is a simple adjustment of one of the
carb. needle valves, but the screws appears to be locked with a
plastic sleeve, and I'm not sure of its purpose. Can it be removed,
and if so, how? Is there another way of fixing this problem?