I'm not a professional, just a homeowner. So I hope you don't mind me posting a question here. I have a Craftsman 4 HP edger/trimmer that is 6 years old. Model is 536.772300. It has recently gotten very wimpy. It starts and runs OK, but the blade stops when it meets minimal resistance. I used to be able to edge rather deeply and angle the blade away from the sidewalk at 15 degrees to make a more pronounced edge. It will cut grass, but now the blade just stops when it hits any soil. The engine RPM's don't change, the belt just slips. I thought the original belt had stretched so I replaced it. No improvement. Is there some adjustment I can make to get more power to the cutting head? The manual doesn't list any adjustments like this. Thanks for your help.