The days of repairing low end consumer string trimmer is quickly coming to past. Homelite/Ryobi (TTI products) don't even sell the piston and cylinder separately anymore just short blocks. This primary due the new design that require pressing the crankshaft apart just to get the piston out and in.
I had a Homelite 4 cycle trimmer in here last week that all it needed was the starter clutch arms. They don't even sell them separately. They wanted the customer to short block the trimmer which the customer wasn't to put that much money into it.