The 661 is truly a killer saw.
I owned 2 copies. The later ones are prety much perfected (DOM after 2016)
I had a 2013 that had the issue with the case cracking at the bar nuts.... what a pia!
In the end I decided to trade the 661 for a Ported MS441 for felling and a 3120 for milling.
It's a bit rich for me but... I have a lot of both felling and milling to do and want to leave each saw set up for it's intended purpose.
If I only had a bit of milling, I would own a 661 as the "One Saw".
When you get it.
Tap in that oiler screw on the bottom and crank up the oil volume. The HO oiler can keep a 36" oiled (in softwoods anyway).
Also,..Read the manual on how to run the carb setting sequence... it will make a big difference in how the saw runs.
Great Saw... Enjoy !!