After some mild porting, DIY mufflers, and a good re-tune......swapped the bars on both to a Sugi-Hara .325 .50 and some Husky X chain. Both saws run much better, maintains rpm's better and both seem to cut much better than stock. The 5105 previously had a 20" Cannon bar in 3/8 .50 but seems to run better with the .325 .50 Sugi Hara bar.