So far very impressed with this unit. Outstanding low range tourqe. I was a little gun-shy about the 4 mix technology. I asked the dealer about the valve adjustment and he said it would at a certain point. The thing that sold me was he said bring it in if I felt it needed it and they would do it free of charge. He also said if there was ever any work on the trimmer that would last over a day that he would give me a loaner. As has been pointed out before, dealer service is very important.