Got a stihl 310 with what feels like too much back pressure...it's hard to pull and sometimes yanks your arm back. Been like this since new. Owner never took it to shop while in warranty to see if it was a warrantable issue. He's an older gentleman, not very big and it's hard for him to pull. It's even unusually hard for me and i'm a fairly young, strong buck. Any tips? I wish stihl used decomprsssion valves as liberally as husqvarna does. Stihl has them only on their pro models, husy has them on most all their models, even homeowner. Any help on this is greatly appreciated.