Had the same problem with my stihl blower...after only one season the fuel line had gone bad...somehow they used line that was not compatible with gasoline. Guess I should have used water.
Took it back to the dealer, and they replaced real fast and without question. They had told me about the known issue with the fuel line, and Stihl put out the equivalent of a technical service bulletin (should have been a recall) to fix this as it could be a dangerous fire situation. Mine was bad enough it leaked, and ran like a turd, as well as hard to start. I'd take it to your dealer and have them look at it and replace the fuel line for free.