Dave posted an answer for this Stihl Hl75 Hl75k Hedge Trim Owners Instruction Manual:
"I gather the black wire is the plug wire you are talking about? the other wire would go to..."
Dave posted an answer for this Sears Craftsman Convertible 25cc 2 Cycle Curved Shaft Weedwacker Gas Trimmer:
"One of 2 things...drive cable broken or clutch spring broken"