I put my original 25" bar and chain back on my saw and it spins fine. With tear down of this saw upgrade etc. and with new bar and chain I was leaning toward something other than the new bar and chain.
Ok... problem solved. The chain was sticking on heal of the bar on top side... the bottom side was fine. Guess it pays to have some small piece of chain to slide thru your bar. $180 for this lightweight bar I took the bar in to Willamette Saw Shop and showed Mike (I didn't buy the bar from Mike he didn't have one at the time, since there is a shortage. I bought the bar from another shop. Willamette is my go-to shop always helpful).
Mike said Stihl has manufacturing problem he's see something. During manufacturing of the oil passages in the bar they plug part of the machined holes with solder. Then finish off he solder in the rails. The finish on one side of my bar was missed. Mike finished off the solder with emery cloth.
I install the bar last night and it spins not perfect but well enough. Mike said to run the chain and it'll be fine if it not totally smooth. Please see the attached picture which shows the soldered, each side of the bar has two holes that are plugged so 4 solder joints.
I learn something … never seen this problem on any my bar purchase in the past.
28" bar on this saw with FC chain run fine with .050 gauge... maybe bit slow but not that I've noticed on valley Doug fir. Hardwood maybe... I just try and keep the chains sharp. Since I rotate out my chains I try to keep eye on the rim sprocket if I'm starting with a series of new chains. I have a 28' steel bar I use sometime I just upgraded to light weight .063 gauge since I'm run more .063 chain on larger saws. The .063 is bigger chain maybe it won't run as well on 28" My rim sprocket has some wear but is not down to the wear marks and drive pins seemed fine to me. I did look at this and I always keep spares, but I understand the concern with the rim sprocket especially the damage it can cause on new chains. I include the rim sprocket just to eliminate the trash with sprocket being the problem. When I stood the bar up and spun the chain thru the nose roller and inspected the both sides of the rails for pinch... this problem really confused me. I have a few saws like 11 but I like this ms361 the best for its weight works well for me. The saw pile picture is missing Mac 10-10, Husky 350, MS034, MS038, MS361, MS461. Oh guess I have old top handle homelite too.