For me it was a Stihl MS 390. I had this saw before I really started using a saw almost on a dailey basis. I had the 390 for over a year. And over the year it seen limited use. After roughly 20 hours of use the pto side bearing flew to pieces. I wasnt to impressed. My old dealer took the saw apart and told me it was unrebuildable. I got it back in a box. So I went to another dealer and got parts and put it back together. I had no clue how to reassemble that saw but I did. I figured if I could put A Caterpillar engine together I could reassemble a saw engine. My uncle has the same saw and it is still running today. That was in 2003 when I reassembled that saw. My second most problematic saw I have is A Husqvarna 385. I had to rplace the carb. The fuel tank vent was replaced and still leaks. And the pull rope jams up sometimes. But it does run good now after the carb replacement. I can deal with the leaky tank vent and pull rope issues. My question is what is or was your most problematic/ unreliable saw that you have or had? Thanks ROB